Thanks for the pic BOUVAL.
I guess there are a few ways to do it, but I would like to have the rotor mounted to the tower or tower plate because of my 2 antenna set-up.
I know if you are going to go with a two mast set-up, the top mast which is supported by the rotor should be as short as possible, ideally 12 inches or less. In my situation I have two antennas (VHF/UHF), so the top mast cannot be very short. I guess I could shorten the distance between the two antennas, and then lengthen the lower mast... But ideally, I would like to go with the single mast set-up with the rotor mounted inside the tower, a thrust-bearing and a single mast.
91XG (47'), YA-1713 (42'), CPA-19, DB4e (37'); Denon AVR-1312