I didnt sheet mine and I dont think you need the strength. I fly off grass too, and I have never had problems with twigs or anything poking through. But that dosnt mean others havnt. The wing is very strong, so strong when my fifty pound toolbox tipped over and smashed on top of it, not one spar broke. The Ultracote didnt even rip either, it did dent a little but that was curred with a heat gun. I built the wing flat and clipped the wings one bay on each tip. I know it looks flimsy when its just bones but youd be surprised how strong it is.