i've done direct comparisons of the Comet and the Clone, on the exact same bike. Frankly i can't tell any difference! so you might as well save the money...
That said, you can buy a series30 clone drive off ebay for $20 to $30 (shipped). for $55 you can get an entire clone kit (drive/driven/belt/mount/cover, shipped). that's what makes it so appealing.
Unfortunately you can't get that deal for a series20 clone. But it's pretty easy to convert a series30 driver to a series20 driver. But you have to spend $30 for the part to do it (which is effectively more than the cost of the entire series30 driver!) and you still have to get a different belt.
At one point you could get a series20 driver off ebay for $30 shipped from AutoZone. but they sold out, and don't appear to want to restock. bummer. But this still doesn't solve the Series30 issues... you can't just swap a series20 and a series30 system (usually).
bottom line... if i could come up with a series30 solution "on the cheap" i would definitely do that. The juggernaut, at $90, is a lot of money... effectively 3x the cost of a comet system. that's why i'm trying to find a comet solution. But Del may be right... you can't fix this Comet system.
I will say the comet series30 clone works *great* on a stock HS50 that turns under 4000rpm. It's when you want to zoom that up, problems occur.