So the OP board can run 4s lipos btw (that is 17V btw) and does it no problem when paired with the Scout or Sabertooth ESCs I ran in my drift Tiger 1. I used x2 3660/3000kv motors on 4s on the 3:1 gearboxes, it was not only fun as heck but destroyed most of my suspension each time I took it out. It was absolutely hilarious taking it on the local car track, people loved it. Due to the height I could never get the top on but man was that lower chassis fun to play with. I know I have pictures of it somewhere, I'll look when I get to my house later and see if I can find it. I think it is like 3+ years old actually....
I've always wanted to go brushless in the tanks (at scale speed of course) due to the larger availability and better specs available for the motors. We could get a much better scale speed with 540 motors and adjusting KV ratings to the tanks. Mainly getting specs for BL motors are the killer for me. I like being about to adjust final speed by the motors. With a gear ratio of 39:1 (you have to use the 3:1 type, the 4:1 type doesn't have enough room to mount on top of each other) there is plenty of torque in those motors to drive as fast as you want and still have the low speed power to creep along. It really helps if you have something like the OP though as there a ton of ways to adjust speed without using things like dual rates which effects the sounds (you don't get the max revs if you D/R the limits) however that is one of the best ways I've found to do it as well and it is super simple to do.