I misunderstood. You want to race Cat 3 open, instead of Cat 4/5 40+. Yeah, that's an idea... You're worried that if you upgrade, you'll be forced to either race the killer Bs or 1,2,3,4 40+, got it.
Agreed with @MadisonDan about jumping into a 1,2,3,4 40+ if you can, but I still think you...