Volfandan,
Bumpfireing requires taping the safety on the grip. It can be done but you have to be careful. Like I said I have done it, but I don't make a habit of it with the uzi. The mac 11/9 with a fake can is easy.
That makes since Gray.....never thought about taping the safety. I know what you mean about the M11/9.....with mine, all I do is hold the fake can and kinda pull outward on the can. The guys at the range swore it was a FA SMG