RPM X skidplates have been
used before on a Flux. The skidplate is flexible enough to bend to the shape of the Flux chassis. The RPM X skidplate comes with cross beams that have cutouts on the end that allow them to sit in the cutouts in the TVPs. Then you just screw the plate onto the holes in the crossbeams and that pulls everything up tight.
I was going to use one on my build but decided to make a custom one instead out of 3mm MDF. Was very easy to do.

Rear arm mud guards help a lot too with keeping the truck clean.