I can can see why omer went for a rail that sticks on instantly but I would still prefer an overnight type glue for that reason. I have pulled one off and started again but I do find it a bit dodgy. Now I just do epoxy rails on carbon like this:
Rons Sea Corner
Which is of no help to phuket freediver sorry.
Again I agree with Ulysses, if its only a 100cm they hardly have any sag anyway. The Nz team do the same no gun butt,no saftey, no muzzle bungy and no shft guide on shorter guns at least.