Nice project. I didn't expect to see a trike with that subject title.
Be sure to step up the driveshaft OD to prevent whipping at high rpm. It looks as though it will be about the same length as an automobile shaft. A hybrid joint where two legs are much longer than the other two can make a standard weld yoke work with the Honda slip yoke if you can rebuild the joints. A thin shaft won't be good even if it is solid, and would likely be heavier than a stiffer tube.
Thank you sIr........
The drive shaft is in the periphery for the moment, but good info to have.......from my research most builders like the JZR in the images have used 2 pillow block bearings to support the shaft to help prevent whipping.... none the less I'm hoping to use the slip yoke between the output shaft and the swing shaft....... if I can.