I don't know what made me try this last night, but the TLR7 Sub I use on my HK45C was laying there on the table. I removed the rail key and screwed it onto my USP Compact.
Its surprisingly very solid and doesn't move at all. Even fits nicely in the holster for the HK45C. The light fits nice and square on it.
Multiple rough draws resulted in no movement of the light. I'm going to try it out at the range as soon as I can, but at this point I don't see it moving.
Worst I can see happening if it does move some is shifting forward towards the muzzle some, but again its impressively solid.
Tell me why I'm wrong

aka in before "your funeral"

Will update in a week or so after range time.
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