RE: Attention Ultra Sport builders!!
That's what I was thinking too. I had to go back and pull out the instructions for the Ultra Sport (I have both the GP instructions and the RCM instructions). When you turn the wing over it needs to sit flat on the TE jig. If it doesn't then you are going to build a warp into the wing. That TE jig and keeping the spar flat on the table is what builds the wing straight and true. If your wing won't sit flat on the TE jig when you turn it over it's got some warp built into it. Until you put the sheeting on the opposite side of the wing a little bit of warp isn't a big issue. Pinning the wing to the TE jig can take that warp out when you sheet the second side. But if you sheet the second side and you have warp in the wing then it's going to be permanently in the wing.
Hope this helps
Ken