Oh yeah, I forgot about that thing!
If you can, trade those FMFs for some Toomey T5s (Wife'sBlaster had some IIRC) or PCs. I hope you aren't a victim of the infamous random impeller destruction. I've heard of some just shearing at random quite a few times. I'd make sure to add a couple dollars to the build budget. Chariot sells one for cheap and they make top-notch stuff.
Whatever it is, just hope it's only on one cylinder. I may have a few extra parts sitting around.