RE: HRC Parts
FYI, you already have a 1/4 throttle. What you want is a 1/5 (or more) throttle.
FWIW, having owned an HRC throttle (which is 1/5th), get the one from EuroRacing throttle (sold by Yoyodyne) instead. Its adjustable to ~1/5, ~1/6, and ~1/7. You'll like it much better.