My advice: If it's warped, start over again. Start with as perfect of a base as you can make. Yes, you can correct some things later with the body filler, but you DON'T want to go through the time and expense of resining, glassing, and bondoing a project, just to find you are not happy with the shape. It's much more cost effective to just start over at the build stage. Plus, if you build a 'prototype' first, then build a second model, you can account for scaling, as well as approach your build with knowledge about the model that will (9 times out of 10) result in a superior model because you will avoid any pitfalls you may have encountered the first time around.
I have built a few PEP projects, and every one I prototyped at least once before moving forward to the hardening stage. But, of course YMMV.