I run a p90 there is no option. Lows are too weird to carry a full load out. "hi-caps' are gravity feed and shooting any direct but down fails. So I skip right to box mag. 1500rds of full auto p90. My 7331 M4 doesn't like anything but hi-caps.
This is more of a cave man perspective though. When everyone plays hi-caps and runs a 10 mag load out and their AEG's ROF sounds more like a blender than a pioneers weaving loom, then we will have caught up to the Japanese Players.