Well, I suppose this is a matter of taste. A short stubby shaft would be called a polar disk mount (in my book) and has the advantage of compactness with the disadvantage of torque across the disk thereby calling for a reinforced polar disk/fork arm or possibly a reinforced polar dis/single off-axis arm.
A long shaft with small diameter conical shaft is almost like a giant diameter (5-6") hollow shaft. Perhaps easier to make but the long shaft results in a high CG for the tube, raising the eyepiece higher than necessary.
So, I compromise in the middle, picking a medium length conical shaft and medium diameter rim. Looks like a scope, too (<-- very important design consideration <g>).
Mel Bartels