Bob,

320cc is pretty darn good to have. I gotta check my kit since I only looked at the wing & fuse for damage check.
Never had experience with VP-20 which is for 4-cycle. It works with vibration, so not really sure how it will work. However, since it was designed for 4-cycle, try it and let us know. Reason that I mentioned VP-30 is because of the higher popularity on 2 & 4 cycle. I have several local friends using the VP-30 on Saito without any problems.

You probably won't need to go full throttle on Saito 82 even for a long vertical.
Good luck!!

IP