Hey guys! Ok 1st those pictures are all the evolution of the same bike! Actually, same bike as in the previous pics!
As far as the rotors go, I have relaced the back wheels (done 2 of em, they're ez) with freewheel/disc hubs from choppersus.com 30 bux! Right now, the latest pic, furthest to the right but b4 the Trike-ster, has a Sturmey 3spd, which threaded on both sides for a freewheel, and I used the disc/rotor adapter which spins on to those same threads, also a chopperus.com piece 10 bux!
Originally, I had used that adapter that I put on the sturmey for the rotor on the front wheel, however as the front wheel hub is obviously threadless on a stingray, and the adapter actually has 12 threaded holes, 6 of which I used to basically pinch the flange between the head of the 6 bolts and the adapter itself!
When I had to use the adapter on the Sturmey, I then went ahead and drilled and tapped the flange of the hub on the 20" front wheel, so the bolts screw right into the flange, I recently scored a bad ass MAC tap n die set, there are 6mm(wide) aluminum spacers between the flange and the rotor, the bolts go thru the spacers then screw into the flange to space the rotor away from the hub & align it with the caliper! It's solid!