I use a 650 x15 yokohama 825 on one car (racing mostly) and 215x15 on another(mostly road). What Craig and Wes use also suits what they do, so what you need to do is work out what your gunna use the car for.
I run Yokohaha Guardex RV 215 80R15 Directionals on standard width 4 stud VW wheels...
They're tall enough to swap with a rear tyre if I get one spiked, miles from no where, then I only need carry one tall standard spare for trips away...
I hate to admit it, but man, I think you're right....
I have bridgestone wrangler TG's on mine (actually 185/14's) which are suited to off road use and have a mud tread. They range in sizes from 14 to 16 inch. See pics below....
I use 225/75R15 Wranglers on the Manx but i will change to 215/85R15`s very shortly. You will need a body lift to run 15`s on the front of your buggy. Before I lifted mine, 185R14`s used to snip the wires off the indicators at full bump....
cheers,
rick