Mechanical brake / Castle Neu problem

Once again, awesome shipping from Mike. Ordered on the 16th (was the 17th here), and the spacer arrived this morning! :D Thanks Mike!

So, now the bad news lol, the spacer doesn't "space" enough lol. Lametastic! :(

I am attempting to use a 15T pinion, but it's about 1-1.5mm too far out to mesh properly, with the spacer on. The 17T is almost there, but not quite, and the 18T is almost perfect.

The spacer has improved but not fixed the issue. Without the spacer, the brake pads/screw were hitting the raised fins on the motor, so the pinion was even further away, so far that even the 18T pinion wouldn't mesh.

With the spacer, I can at least get the 18T to mesh (its probably a tiny bit too far out but I can live with that).

Anyway, the issue is that the 2200kv motor is like crazy over geared with the 17T pinion, so I can't imagine how crazy the 18T would be. The 15T is MUCH nicer, more controlable, and the amp draw and battery life is excellent, unfortunately, I can't get it to fit with the mech brakes.

So, is there anything I can do to make it fit. I assume I'd have to make a thinner spacer to add to the RCM one, like out of 3mm Aluminum or something like that, or perhaps cut some material away from the end of the can?

Here's a photo