Problem with RB TM323 (Revo) and Sullivan "Tiger Drive"
 

I installed the O.S. .18TM in my Revo but due to a cold Winter here in the Northeast I never even got to run it before RB brought out the TM323. I'm so happy with my RB C-5 Circuit engine in my 1/8 on-road Serpent 950R that I pulled the brand-new O.S. .18 and bought the RB TM323 with the 01900-121 backplate which RB markets as a "REAR COVER TM728 Tiger Drive comp (sullivan)". I removed the original plastic backplate (#01901-323211) but the new cast backplate/adapter won't fit (it seems too large).

Has anyone else experienced this problem and can you provide some advice?

Thanks!!!