I have played around with modified designs quite a bit.
here is an example from my album(sorry thumbs don't work for me and here they would be appropriate)
Both of these are done as "longwoods" but the lower is with the designer kit{PKMONPAR from Woodturningz and the one with the antler is a slimline.
In modifying the designer, the "b" mandrel works well as it is made for the 8mm tubes.(make your own bushings)
As far as "hiding" the gold ring the tranny screws onto I grind them off or turn them off to leave a slight shoulder to nest on the bottom blank's tube and countersink the bottom of the top so it fits over it.
A similar modificaton can be done with the Perfect Fit from the "b" company.