A little more progress:
1) Glued a tapped plastic block to the bottom of the ESC and re-heatshrunk it to allow me to mount it.
2) One of the first things I noticed upon receiving the GTP is the the chassis is quite "flexy", even with the existing front and rear braces. This is presumably from the lack of kickups on the sides. So, I made a top plate out of 6061-T6 Al, and doubles as the ESC mount. VERY sturdy now! I also cut off the excess brake cam shaft so it sits flush with the top plate (gotta make sure nothing rubs on the power wires).
On a side note: I was a little concerned that the HV-110 wouldn't have a high enough current capability for this project, so I looked up the
specs for the FDS5672 FETs. Turns out they are rated for 60v, 12A, and 0.01 ohms each (@ 25*C). There are 108 of them on this ESC. And seeing as how there are 36 of them on at any one time (18 on the + coil, 18 on the - coil), that brings the rating to 216A and 0.00055 ohms! Even derating the FETs for 75*C (167*F), they are still good for 130A. And that is continuous current. Peak is much higher depending on how long the burst lasts (ex: if the burst is 0.1s, the rating is 40A each). Seems a tad underrated compared to some of the other ESCs out there.