Optimum Pyramid Winter Inner Tent Material

Strength shouldn't be too much of a concern, as the canopy won't be weight bearing. So long as you pack it carefully, the lightest fabrics ought to do just fine. I'd lean towards the more breathable ones, to minimize condensation. Tigoats Nobul1, for instance. Given that you'll be using a lot of material, a 10d fabric will actually save a decent amount of weight over a 20d. If your mid has closeable peak vents, some mesh strips up near the top might be a nice option for increasing air circulation if desired.

I would ignore water resistance. All it will have to deal with is occasional drips from condensation or frost dropping on it. And as DC points out, strength is not needed much. Maximum breathability and minimum weight , in that order, would be my criteria. A little weight penalty to get more breathability will likely be worth it in terms of livability.