Does anyone here have a link to video instructions for the installation of the Mossberg 590a1 heatshield (16335P)? I've found one video for a generic 500 heatshield install, but it didn't go into too much detail on how the spacer is supposed to be cut and placed. Is it supposed to be cut to an exact length so that the heatshield doesn't slide forward at all during shots? If so, anyone have tips on how to make it fit exactly? Also, anyone have any recommendations on an aftermarket safety button replacement?