Joe, you might think about putting the compressor in the garage and running some air pipe down to your work room. I picked up a kit from Northern Tool that uses 1/2" nylon pipe with push-in fittings, makes plumbing pretty easy.
Building the empennage down there won't be a problem, space-wise. Before you start the wings, though, just be sure you can get a 4' x 10' x 8" object ALL THE WAY outside without bumping into anything. It would really suck to have a rude surprise when it came time to move the wings.
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)