FYI -- I just installed a set of e-flite EFLH1205 training gear designed for the BCX series. I simply mounted the plastic hub with velcro to the botton plate of my REX 450SA and inserted the 4 ping pong ball posts into to the hub and through the main gear of the rex and it works great ----- It provides much needed stability for a novice like myself -- I can hover now with additional confidence !!! Its worth the effort.
$9.99 investment is worth every penny !