Well, I've been tinkering around (and learning how to do 3D drawings... quite maddening if I do say so) with custom TVPs for my Savage Flux 5B to use a center diff. Truggy is also a tight squeeze length wise when putting the batteries inline between the TVPs. The other issue is the in using either the truggy setup (or even the custom mount from RCM) is lack of gear reduction due to running 43/13 or 29/9 (bullet proof diffs) front/rear diffs as compared to truggy's 43/10 diffs.
Anyways, pb4ugo in his thread came up with a very nice solution. I'm not a huge fan of the Revo slipper, and may eventually run a Slipperential so revamped it slightly from ground up. So here is the open center diff "gearbox". Like pb4ugo, the gear reduction comes down to the standard flux so you can run standard Savage/Flux diffs.
Basically the plan is to run a 46t center diff gear, a 12t pinion off of that and then a 25t (biggest mod 1 pinion I can find) pinion as the drive gear. A 17t pinion on the motor comes out very close to the Flux FDR (15.70386 vs 15.56956).
This puts it at about a 17/18 pinion with a 1600kV motor on 5B wheel/tires and running 6S. Or a 15/16 pinion with a 1800kV motor.