Its after Sept 1 now...Im sure Rob will have the rules up on the USVTA website soon.
If you show up at any of the tracks you listed and they have a USGT class there wouldnt be much that would change on your car...if they changed any rules for their track.
Also having done some more track running the 21.5 with open esc is very close to 17.5 with limited esc....so if you choose either power plant you will not have an advanatge either way.