Got a chance to test the changes this afternoon, and the results were good. The airplane will now turn left on the ground (when it feels like it), and rolls out a lot straighter on landing. Moving the CG to 4" had no noticeable effect. I'm thinking about going to 4.25 like someone has already suggested here.

I'm still having lots of trouble nosing over on landings, after the tail drops and the speed gets low. I'm thinking it's a combination of our downhill runway and the crappy Hangar 9 wheels. I've found these at Tower Hobbies that look closest to matching the originals. They have a 5mm axle hole, and the axle on the Camel is around 4.25mm. So many of the vintage wheels have 1/4" holes, I was surprised to find these.

http://www3.towerhobbies.com/cgi-bin...&I=LXWAB2&P=SM