I've been racing with freewheels. 18t on one side, 20t & 22t on the other. Only annoying thing is repositioning pads when jumping from one extreme to the other, only takes a couple of minutes though.
Look at bmx race hubs if you want splined freehubs, Profile Racing should have something in 120 OLD
Hmm. Have you ridden sscx with freewheel? How was your experience?
I rode last season with 130mm hubs I my 120mm alu frame, but I am worried I'll break the frame