RE: Sig 1/3 Spacewalker
I have a 1/3 Sig Spacewalker and I'm running an older Quadra 42 in it. This engine is a great match for this plane. You can get a US 41 (same as the Quadra 42) for pretty cheap and it will fly the plane great. It has enough power to do scale aerobatics and get you out of trouble, but not too much that it doesn't seem scale like. It is a great flying airplane and one of my favourites.
I've flown one with a G-45 (had a little more power, but generally handles the same) and I've seen one with a G-62. The G-62 provided much more power and allowed the plane to do more extreme aerobatics.
Mine is covered in Supercoverite and sprayed with Latex.
Grizak