Jamie,
You'll love the Aircore. I kind of wonder why it doesn't get recommended more often. It has to be the toughest trainer on the market. It may be because it is so durable that you can try flying it without an instructor so most of the old timers who live to instruct put it down when asked about it. An instructor is much MUCH more necassary if you have one of the balsa planes. Or it could just be a bias against it because it is unconventional in materials and construction. It is a little heavier than it's balsa twins but if it's not that much of a difference. When I started looking at RC planes I snubbed the Aircore at first. I thought, plastic airplanes are for kids, I want a balsa plane. After a couple months of building with balsa from scratch the plastic plane started looking pretty good as a trainer. I have a bunch of 4mm coroplast laying around too (old real estate sign's) and I wanted to learn more about SPAD's and figured the Aircore would teach me that too, and it did. Just wish I could find some 2mm signs now.