My camper is a 9-1/2' floor, and overhangs by about 20". My extension puts the ball right at the rear of the camper, which is fine. It doesn't have to be past the bumper unless you have a weird trailer.
For a couple years I didn't use an extension at all. It was tight but it worked well, and only hit when the trailer swung over too far while I was backing up.
You should not need anywhere near a 34" extension with only a 10' floor camper.
With a 3" receiver, though, I would make a extension from 3" 1/4" wall square tubing, and use a 2-1/2" shank for the trailer. No reducer sleeves, less slop. That's basically how I did mine; 2-1/2" square tubing, 2" shank, no reducer, no slop.
