I think you're mis-reading the specs.
On series20, there's a 13 degree angle on *both* sides. it's symmetric.
On series30, there's a 2.5 degree angle (basically flat) on the non-moving side.
So on a comet system, you just change the non-moving sheave, and you can go from series20 to 30 or vice versa "pretty much".
the juggernaut is potentially the same way.
here's the series20 data... note it says "symmetrical 26 degrees" (which means 13 degrees each side.)
http://www.pinrepair.com/minibikes/comet20series_man.pdf
on the series30, it's "20.5 degrees asymmetrical." which breaks down to 2.5 degrees on the flat side and 18 degrees on the moving side.
http://www.pinrepair.com/minibikes/comet30series_man1.pdf
now is 18 degrees versus 13 degrees a lot? well i guess. but in the case of the juggernaut, if you just re-made the non-moving sheave to be 13 degrees, it could be used as a series20 (and probably work just fine that way.)