Oops, got locked out. Okay, here's my response:
1st of all the holes drilled in the clip should be on the tight side. You will pre-run the screws in the clip to cut their own threads before you mount on the terminal. Check for any burrs afterward. The hole in the terminal is just right as is. Not to tight, not too loose. When you cinch down the screws, they Will be secure. So let racer decide as I'm sure they're looking on. Free advice here, free screws from your old motors, but I think if Mike can provide pre-drilled clips that will allow the tap screw to pre-cut threads, that's where he can make a couple bucks.
If the self tap screws don't stand up, then standard thread screws and nuts will do the job.
A wire inserted sure may be easier and work okay, but again, it won't assure that the clip will not move around, vibrate on the terminal. Might be just fine for most applications. I'm sure going to be experimenting and welcome to see other racers results.