So I've thought it over a bit more, and I have a stronger opinion now. Keep in mind that I'm not a marketing guru, but I really want to see your business succeed.
If your goal is to expand your business and gain traction in the market, I would strongly advocate against producing a 1/8" pad as many others have suggested. My thought process is this:
1. The market for these ultra-thin 1/8" foam pads is already saturated. Off the top of my head these are already sold by: MLD, Gossamer Gear, Prolite Gear, and Suluk.
2. A 1/8" foam pad is sort of a fringey item. It's really only useful as a marginal supplement for warmth, a pseudo-groundsheet, or protecting an inflatable pad. As a groundsheet and warmth supplement, the bulk and annoyance doesn't really justify the benefit. I can't speak to the inflatable pad aspect since I gave up on those things.
3. Even though a 1/8" pad made from your proposed foam is an improvement over existing Evazote pads of the same thickness, it would be a relatively marginal one. For example, assuming correct weights and R-values, a 1/8" pad in your foam (72" size) would be about R-0.67 and weigh 2.0oz. Existing pads of the same dimensions are ~R-0.42 and 2.7oz. This is a nice improvement, but as you scale up the thickness, the differences become much more substantial. Consider the difference between putting a $10 item on sale for $5, and putting a $200 item on sale for $100. Proportionally, they are equivalent. But the second looks like a much better deal. It's the same concept with the pads--the weight savings appear greater in real terms as you scale up in thickness.
Given these three things, I would say that offering a 1/8" pad would be a weak, conservative move. The same goes, to some extent, for a 1/4" pad. However, this thickness would exist in an awkward no-mans-land: it's too thick and heavy to use as just a groundsheet, and too thin to use on it's own.
If it were me, and assuming the weights and R-values for this foam are accurate, I would try to develop a pad marketed as a "Ridgerest-killer". Lighter. Warmer. More durable. More comfortable (Evazote has a memory-foam quality to it, Ridgerest foam is fairly stiff--plus you describe this new foam as even more comfortable than traditional Evazote). Here are my thoughts:
1. As described above, it would be significantly better than other existing products of comparable function, namely the Ridgerest. A 72"L/20"W Ridgerest is 5/8" thick, weighs ~14.0 oz, and has an R-value of 2.8. Again, assuming the numbers you gave are accurate, the same size and thickness of your foam would weigh 10.0 oz and have an R-value of 3.75. That is an insane improvement.
2. The Ridgerest is an established item, and is widely used by all sorts of backpackers and other outdoor enthusiasts. If you introduced an item that was directly comparable, but clearly superior to a trusted item like the Ridgerest, it would be an easy and comfortable transition. On the one hand, you capture traditional backpackers who are used to this type of sleeping pad. On the other, you pull in thru-hiker types and ULers for whom foam is just slightly too uncomfortable and heavy compared to the rapidly improving and sexy inflatable pads, but who also hate the hassle, high expense, and unreliability of inflatables. In short, this would have much broader appeal and a much higher-ceiling in terms of capturing market share.
3. In terms of thickness, you would have a couple of good options. The 1/2" would be the lightest and have a comparable R-value to the Ridgerest (which is just about ideal for hikes like the PCT and general summer and late spring / early fall use). However, you suffer from the problem that it's thinner and therefore less comfortable than it could be (may be more of a psychological issue for people--they may be reluctant to go thinner than a Ridgerest). Secondly, (if you could get it manufactured in this thickness) you could match the Ridgerest thickness of 5/8". This makes it easy to make a direct, one-to-one comparison to the existing and trusted staple (Ridgerest), only it would be lighter/warmer/more comfortable. The R-value on it (~3.7) would be perfect. Lastly, you could go for the 3/4" thickness, which would have the marketing advantage of being much warmer and thicker than a Ridgerest, while still being 2.0 oz lighter. Each of these has their advantages, but if it were my decision, I would go for the 5/8" thickness as a happy medium. Plus, you are going for blood and making a statement about the superiority of your product.
4. Also, if I were in your shoes, I would push this as your flagship product. If the foam material is indeed as you describe, it is filling a massive void in the market and is a major leap forward (in my opinion). It could become the defacto standard for people like PCT or AT hikers, just like ULA packs did (noticeably, by striking the happy medium between ultralight and traditional backpacking, just like this foam pad would). From there, it would spread to other hikers. In addition, if you have one flagship item that is associated with your name, it builds trust in your brand and draws people into buying your other products.
5. Aside from the significantly better objective qualities of this pad, you could differentiate it by giving it a distinctive name and color scheme (I don't know about the extra production costs of dyeing the foam, you would know better than I). Everybody knows and recognizes the woodsy green color of the Ridgerest, and it is instantly recognizable if you were to see it on the outside of someone's pack. I think a bold but restful/inoffensive color like indigo or cobalt would be awesome (you'd have to make it a different enough shade of blue compared to Walmart blue foamies). It would look like a million bucks if you could go two-tone: a grey/silver on one side and a deep blue/green or blue/purple on the other (again, this may or may not be feasible depending on your supplier. Here's an example:
You may also be able to cut out or imprint a small logo into the foams somehow. Anyways, my thought is that if you have a distinctive look to the product that generates interest and questions on the trail, it would help it catch on faster. Also, the plain blacks and greys are extremely dull and generic (looking at it from a marketing standpoint).
Sorry for the long post, but I think you could hit a grand slam if you went for the "Ridgerest-killer" approach. I know it's probably different than your vision of mainly supplying accessories and so on, but I think that this slightly more assertive approach would be a good move in terms of growing your business. Plus, the risk of this more focused strategy is not much higher than the alternative, which is offering a slightly improved version of existing Evazote pads (i.e. 1/8" or 1/4"). The rewards are potentially huge (IMO). I'd be interested to know what you think about this.