Oh no, bad news mate.
How deep are the holes? If you have a .050" driver, prod it down the hole, put your thumb where the hole ends and pull it out - that should be the length (or next smallest) your ballstud needs to be.
But saying that, I would have thought you'd get away with as long ballstud as you'd like in there
So, here's what do do - seeing as the material on most cars is prone to stripping threads when heat is generated by cutting new threads. Use the driver to screw the ballstud down, but don't tighten it, leave it approx 1mm from tight - and then do the other side, the same, leave it 1mm. (I bet you can feel it quite hot, this is because it is cutting new thread). Let it feel cool to the touch, and then tighten it, only touch tight.
but if your ballstud is too long, that'll need addressing first. Doing the thing above when tightening any screw/ballstud into Losi plastic is always a good idea, as the heat from cutting new threads can literally melt the plastic and that strips the threads.
Chris