Radials:
DX Engineering recommends 32-60 radials, length doesn't matter if they're imbedded in the ground. But that's for a ground level mount.
They recommend you do the same if mounted more than 3' above ground, but that they be angled downward at 45° and they be cut for 1/4 wave length, a portion for each band.
At the same time they admit it's "may" not be necessary. My experience, limited as it is, was with my pickup truck and a Hustler mobile antenna. No radials there and it worked great. Could have been the whole truck was just the right lenght to form a ground plane. I like to think of my vertical as just a dipole only up-and-down. So if I drop 4 wires, each 1/4wl for each band then that should work.... right. My plan is to put it up naked and see how it works. If I'm not happy, I can add a few "tuned" radials draped on the roof.
Tower:Here's pictures of the side mount where you can see the DX Engineering Genius clamps, which are quite a substantial and do a great job of creating a rigid side bar. Then I use pairs of stainless saddle clamps to mount the side bar on the tower.
And before I remove the top section here's the tower in all her glory with a puny Ham Stick on top and three little radials hanging down.
44 states now, finally got Nevada.