Don't know how far along your wing is, but looks like you already have the sheeting done. One thing you could try is re-enforcing the wing with some of that carbon fiber wing reinforcement tape that you CA to the surface of the sheeting, then sand smooth. If you can get the wing held down perfectly flat with some weights or something then apply your CF to the sheeting over where the spars are located, then that should help. Here is one technique I found that I will be using on my wing for a bipe I am building.

Over the top and bottom of wing, inline with the spar location, take a 1/2 or 1" wide sanding block, depending on how wide your CF strip is, and lay a long drywall ruler over the wing as a guide. Then sand a very slight channel along the length of the wing where the CF will lay, thus allowing it to lay flush with the sheeting. Then lay your strip in place, and thin CA the whole thing down through the CF itself, since it is usually pourous. For super strength, you can also apply a VERY thin layer of epoxy to the channel first, instead of using CA, then lay the CF into the channel, and squeegie out as much epoxy as you can to make it flush with the sheeting and minimize weight. I will be using epoxy myself, I love epoxy. It doesn't add much weight if done right. That CF strip is only about .007" thick, and needs just a tiny bit of epoxy to do the job. Then spend some real quality time and sand smooth carefully.
Once it all sets up, the Carbon Fiber strip should help to straighten it out. It may not be perfect, but you will have one strong wing when complete.

Patriot