Making prefabricated fiberglass skins is an interesting way to go, but I would absolutely make a smaller model first to get it dialed in. In my experience I need to do anything at least 3 times before I really know it, the first time it might be usable but I will not be entirely happy with it, the second time it will likely be usable but there will still be some things that I know I want to do differently the next time. You don't want to do all these experiences with an 8 foot plane, try to find the interesting part of making a smaller model first or make the stabilizers first at least with the same method so you don't put a lot of work and time in to a still born project - it will drain you doing that.