Mike,

I am building the same plane and I'm to the point of mounting the retracts. you can find my build documented here:

http://www.rcuniverse.com/forum/m_28..._1/key_/tm.htm

As far as building surface goes, I currently use a 3'x 8' peice of modular furniture desktop that was surplussed from work. It is dead flat and really heavy so it doesn't move around. But to build on, I got a sheet of 1/2" of the pink builders foam (what they use to sheet the sides of houses) and secured that to the board. It works really will and doesnt' crumble like ceiling tiles can.