A good idea is to drill a countersink in the glass for each bolt so that there is an "o-ring" around each bolt head. Do not use 5200 because this will pull off
gelcoat when (not if) the hardware is removed. 4200 is better, butly tape is the best in my opinion. Tighten the bolts once, as if you do it a second time, you can break the sealant bond. Step by step with pictures on Mainesail's site. If the deck is cored, be sure to pot the deck with epoxy to avoid future rot in the core. Extreme stickiness of 5200 is not needed, but ability of sealant to elongate as hardware moves is , and probably stanchions move more than most hardware.