First, your designs look great, Jason. They are very tidy and polished looking. These are some of the most clean and handsome minimalist 1-person tarps I've seen.
But, I disagree with a few of the minor details in the spinn vs. cuben Pros/Cons accounting.
First, I just want to emphasize that "0.75 oz" spinnaker doesn't weigh 0.75 oz/yard. I cringe whenever I see the "commercial weight" for spinnaker used instead of the actual weight. There is a convention (that has nothing to do with the sailmaker's yard vs. textile yard calculation) that spinnaker fabrics are sold with nice, round nominal weight labels that are gross underestimates. I have some "0.75 oz" spinnaker that weighs 1.8 oz per yard (and 1.4 oz per sailmaker's yard). This arose from competition between sailcloth mills and sail lofts and deceptive marketing, and it is now considered conventional. There are companies making "0.4 oz" spinnaker that generally weighs about 0.9 oz/yard (about 0.75 oz/sailmaker's yard). The 0.75 oz cuben, in contrast, actually weighs about 0.75 oz/yard (a little less, even), and, as you say, Jason, it is much lighter than the "0.75 oz" spinnaker.
The 0.75 oz cuben has a warp breaking strength of about 100 lbs per linear inch. This is nearly four times the warp breaking strength of a typical "0.75 oz" spinnaker. And any pinholes that appear in the 0.75 oz cuben will be microscopic and it will still be more waterproof than a typical spinnaker in the 1 oz/yard range. So, I think most people who have any experience with these materials will balk at the suggestion that 0.75 oz cuben is less durable than "0.75 oz" spinnaker.
Also, spinnaker can be quite loud, depending on the composition. The classical "Spinn" (ie. Spinnntex) that has been used for backpacking shelters (Spinnshelter, etc.) is polyester, and this material is famous for being ridiculously loud (much louder than cuben). Nylon spinnaker is quieter because it is more stretchy, but the cuben still is not so loud (once tautly pitched) that most users consider it a problem.
Despite all this, it has to be conceded that no cuben tarp could match the smooth and color-coordinated beauty of your spinnaker tarps. They look great.