The ROF will be similar to a full charged large 8.4v 3600mAh NiMh battery. A bit "peppier". Not a fast as a large 9.6v pack, but about the same as a small 9.6v pack.
So if your mechbox can survive those batteries...it'll be fine.
BUT...careful of long sustained strings of full auto with a "little" lipo like that. They can get very hot as they discharge. Short 5-10 shot bursts are fine. Near unlimited semi has been fine.
I had a runaway mechbox shoot approx 1000 rounds full auto while hooked up on that battery. The mechbox was fine...the wiring/motor were hot (as they would be anyways with any battery)...but the battery was really, really hot. Hot enough to the touch to think, "WOW...that's not right". The pack seemed fine, but I wouldn't do that again on purpose.
It's a good batt and tucks away in the smallest of places. Just use your head.