center diffs?
 

are some center diffs shorter or longer than others output to output on 1/8th scale?

Yes.

large diffs - Hot bodies, Ofna, Kyosho 777 and older
Small diffs - Losi, AE, Mugen, Xray

Very small center diff - Kyosho Mp9

Hyper 9 CD's are small or very small (not sure?)

Chris- do you remember which CD Mike used when designing the CD mount? Mugen i'm thinking...

The slipperential is v. small btw. Much shorter than the few ofna's I have

asociated is large.
Slipper is small ( to be universal )
Mike's cd is large ( to be universal )

okay, to fill in. i'm doing a conversion on a cen gst, and i have here a gs storm sut diff, and it just barely too tight for using the axles for center shafts which would make things easy easy for me.