You need a flat chassis, so if you were to grind out all the X-5 stuff to create the room you need, you will end up with a weak, flexible and brittle flat pan to start with, and the front end would still be impossible to flatten due to the complexities of it not being 1 piece.
What id suggest, is start with something that has a flat chassis and adapt it backwards.
Soooo.. start with a B44 completely, and then modify the front inboard hinge pin mounting points to match XX4/X-5 positions, then fit Losi wishbones and stuff, but B44 driveshafts (to match to the diff), then fabricate a CF tower to the B44 mounting to match that of the XX4 positions, same with camber link positions.
For the rear you may be able to get the XX4 tower on with some modifications/strengthening, and same with the inboard hinge pin blocks. But at the minimum then fabricate blocks to match geometry, mount to them the XX4/X-5 rear wishbones and so on, but with B44 driveshafts again. Then fabricate a new rear tower again to match XX4/X-5 mounting positions.
With what I have suggested, what you end up with may end up looking a lot like a B44 still, but running many Losi parts on each of the 4 corners. The thing is though that the CF towers and stuff will be stronger and probably cheaper/easier to source than the XX4 ones which are more brittle. You'll also be able to run B44 shell.
If there was a slider between B44...........X-5 I think I have just moved it a few notches closer to the B44 just purely because of do-ability with your ideas.
Your plan: B44.................................*........X-5
My suggested plan: B44..........*...............................X-5
The other thing to think about, is to move the motor further back, to compensate for the loss of weight there with the use of Nimhs, Perhaps even something much like the pre Worlds BJ4.
