I run 1 thin pad between the shorty and esc. I have my ESC mounted on the chassis, not on the t plate. I also like the weight centered forward like this. My ESC has never moved or been damaged running it this way. 1 thin pad is good enough.

If you want to build a stop I think the easiest way would be to modify the battery brace maybe drill a screw and a nut through it for a stop or add a stick weight to the rear of the brace. I was going to play with that but didnt need too.