That makes sense. I was thinking that mounting at the rear, it would only be used when the jeep is sitting still, by either of the gunners aboard, leaving the driver free to focus on driving. Once I started fitting the ammo bin for the M134, I realized this was going to be a 3 man crew, and if I loaded it out with packs, the M107 either is omitted, or moved toward the front.
I also have some AT4s to strap to the engine hood.