Larry,
The key to the front mount without the rear bearing is a strong mount wall. Bob has a composite mount, I have used 3/16" aircraft plywood (no 1/8" lite ply). I construct the nose with 1/32" ply doubler and install the mount wall with epoxy and small 1/8" wood screws through the plywood doubler. I also construct a box around the mount wall to give some extra stiffening (might be over kill). Were we had trouble with the front mounts (probably the rear mounts also) was using 1/8" lite ply mount wall, this allowed the motor to move due to prop precession forces, once you added the rear bearing it stabilized this. The strong solid single front mount does the same and allows for a simpler motor mount.
Best, DennisT