Okay, the BP-21 is a pretty high-RPM motor. It's rugged as heck, with a thick steel bell, and comes with a decent aluminum mount. However, it is wound such that it will pull a surprisingly high number of amps. On small Lipoly packs like you're describing, it is limited to about an 8" prop, and that's not the greatest for 3D, but it will work. The BP-18 esc works, but it's notchy and makes it very difficult to hover. I have one in our shop "loaner" R3D, and there's no throttle setting to hover, just "climb" and "drop" with nothing in-between. Maybe some other examples are better.

If you still want to try these parts, you could email us at [email protected] We have an in-store sale on these parts starting Monday. Probably the best way to utilize the 21 would be to re-wire it for lower RPM configuration, but I haven't tried that myself.