Hi Dougsr.874,
Enjoyed our conversation on the phone yesterday. It isn't a secret that the 4G has also had its share of issues. If you elect to use the 4G be sure to do a little research concerning the clutch, freewheel, and ratios.
If you decide to continue with the "hoot" single chain drive, I would suggest finding a quality chain to replace the existing version, and design some way to keep the chain tight while in motion. I am aware of a few attempts to fix the shorcomming of the primary chain drive system from "Hoot", but it will require constant service. If possible install a spring loaded idler on the return path of the chain, but remember the chain is turning at motor speed [very fast, up to 8000 RPMs] and it might be wise to use an idler with a chain sprocket as opposed to a flat idler. It is also important to locate the idler as close to the front sprocket as possible to make the chain wrap around the smaller sprocket.
I know of a couple attempts to install a HD Sportster guide, but the chain managed to cut a path into the guide and allowed the chain to jump the front sprocket.
As we discussed on the phone, the best solution is to replace the crankshaft in the motor to the longer 5/8" shaft and use the Stage lll gearbox.
Keep us posted on your progress.
Have fun,