J-man,
I have flying my Dazzler ARF with an OS FL-70 for a few months with that
exact arrangement. No problems of it working loose. I just pulled that motor
off the Dazzler to try it on a Sig Skybolt (same mounting) & when I removed
the motor from the mount, it was still solid. I'm going to add left & down thrust
using washers behind the mount.

Goog Luck!

Johnny C