My experience is that the rubber shrinks a bit over time. I don't pull it taught before I mark it and cut. I sort of push the other direction to make sure there is no initial stretch to that rubber. When it shrinks it is not too small.


1947.2 GMC 1/2T SWB panel
1947.2 GMC 1/2T long bed
1948 GMC 1/2T short bed