"Hey did you find that the tent poles sunk into the ground at all?"
Yes they did an inch or two when I really tensioned up the ridgeline. It would probably be prudent to use a bit of wood or rock under the poles if you're camping on soft-medium ground and desiring a night tight pitch. A cap for the end would be ideal. In my case, I plan to pretty much always use hiking poles.
"I don't own any shelters with a silnylon floor, but my understanding is that they aren't very waterproof, a groundsheet is usually required to protect against punctures, and they are slippery. I've never used a groundsheet, but the floors on my shelters are all PU coated nylon and something heavier than 30D. Concerns with waterproofness and durability continue to deter me from purchasing a TT, even though I love some of the new designs.
You're sorta mixing two things...the fabric (ie. 30D nylon) and the coating (ie. silicone or PU/polyurethane). Silcone coated nylon is often called silnylon.
30D Nylon - 30D Nylon is a fairly light nylon, but with reasonable care it does just fine as a tent floor without a ground sheet. You don't want to pitch on gravel driveways, but otherwise it'll do fine as long as you do a quick scan of your camping spot to avoid big sharp sticks, broken glass shards etc. My last 3 or 4 tents have all had a 30D nylon floor, and I only ever put a small hole in one when I car camped on a gravel pad, despite never using a ground sheet. If you're hard on your floors, you could consider a 70D nylon floor instead. SMD offers both. FYI, when nylon is called '30D' it refers to the thickness of the individual strands of nylon that are woven together. The higher the number, the coarser and stronger the fabric (and heavier).
Coating - Virtually all mainstream tent manufacturers use PU (polyurethane) coated nylon. The PU coating gives it a bit more strength, but mostly it's there for waterproofness. Depending on the thickness/type etc of the coating, the waterproof (ie. hydrostatic) rating varies from lows are 1200mm up to 10,000mm.
A lot of cottage manufacturers use silicone coated nylons instead of PU coated nylon. I'm not sure how this originated, but it might have been because light/low denier (ie. 30D) nylons may have first become available in silicone. Mainstream manufacturers don't' use silnylon because it can sustain a flame if you light it on fire, so it doesn't meet some fire regs in somes areas, whereas PU nylon will self extinguish. Like PU coated nylon, the waterproof rating varies but it's generally lower around 1200mm but sometimes it's 2500mm. I'm not sure what the actual spec is for TT's silnylon.
The weight of silnylon and PU nylon is quite close for the same durability of nylon (ie. 30D). 30D nylon weighs about 1.1oz per square yard and after it's been treated with silicone it usually weighs around 1.4oz. PU coatings are slightly heavier, but we're talking about a finished weight around 1.5oz or 1.6 I believe....so the weight difference for the floor is maybe 0.2 - 0.4oz total.
- As long as you aren't' camping in puddles, the waterproofness of a normal silnylon should be enough to keep the water out. I've only had trouble with a 1200mm rated floor once and that was an older tent (non-TT) camped on snow.
- 30D nylon (whether it's silicone or PU coated) is durable enough to use without a groundsheet as long as you exercise reasonable care.
- Silnylon is slippery, you'll want to dot the underside of your pads with silicone to prevent sliding.
- On average, silnylon is less waterproof than PU coated nylons
- On average, silnylon is a hair lighter.
I personally prefer PU because the weight difference is negliable and it eliminates the slipperyness. The increased waterproofness is more of a side bonus in case things go sideways and your campsite floods. This is for tent floors, for the fly it really doesn't matter, although some might still prefer the PU because it doesn't hurt to have a more waterproof fabric.