Hi Bobby,
Thank you very much for your praise and confidence in the SC20.
The ARC22 system design has many goals/uses. If you have an old worn out SC20, all hardware and rigging from the 20 is interchangeable to a set of bare 22 hulls. Everything on the 22 is the same as the 20 including centerboards and rudders and gudgens and tramp tracks and trampoline and beams, etc. The 22 hulls are simply 20 hulls with two feet added to the bows to increase the hull fineness ratio and increase the pitch stability. The self tacking jib is an upgrade that can be part of a spinnaker pole set up or without the spin pole simply use a foot tube from the main beam to the jib tack point.
The spin pole set up on my 20 is identical to the one on the 22. The lower pole position leads to a longer luff jib and taller spinnaker. Long luffs are faster. Along the luff of a sail is where the action is; that's where the forward pull is, front third of the sail.
You don't have to engineer anything to put a spin pole on your 20. Just copy the 22 or buy the parts from Aquarius Sails. E mail me if I can help.
Bill