Closed end rivet in test application

Question is whether the M4x16mm bolts are too long for the closed ended rivnts.

I have found that M4x12mm stainless steel bolts (and probably the M4 x16mm bolts supplied) were observed to noticeably stretch in a test application where the cork gasket was compressed 50%, and this occurred at torque levels well below 17.7 in-lbs. Realistic tightening would entail a compression of the cork gasket not more than 20%. This, rather than torque should be the tightening criteria.

The following measurements is that the tip of the M4x16mm bolt is 21.6-18.7 = 2.9mm from the (external) end of the closed-ended rivnut. With a wall thickness of ~1mm this implies about 2mm clearance internally. However this test case is right near the limits of reasonable cork gasket compression.

The M4x16mm bolts are fine.