Can't use mechanical brakes???

[mk351e]

So, I now have everything for my Muggy conversion except the eternally backordered batteries (see my next post!), and I'm chipping away at it every night. I planned on using mech brakes, but I can't seem to make it fit! I'm using a Tekno Neu 1515, RCM motor mount, AND the RCM Neu spacer (adds 4mm), and no good. In fact, I can just make my 18T pinion touch the spur, but not mesh. I even messed around with some of the brake hardware, but still no good. I was thinking of busting out the dremel, but I dunno.

Am I missing something here? Are mech. brakes THAT much better? Or is there some sort of secret here that I'm unaware of?