You don't need to worry about it until you have the spars/ribs all framed together and hanging on the stand. Then you can attach the bottom support bracket for the rear spar at the right height, clamp them down and get the twist out for match drilling/riveting.
I'd like to fashion the forward spar support brackets while I'm waiting for the wing kit to arrive, and I want to be sure it's high enough off the ground - and of course, not too high either.
I don't have the dimension but I put the front spar at shoulder height for a RV-7 and that worked great. I also did both wings at once which made it go quicker