Anyone who has been around boats for a long time knows what the back side of a deck looks like when the backing plates come off and the fitting has been leaking. Butyl tape, a deck cleat that sees tremendous loads, no countersinking and yet 29 years of service later and BONE DRY! No rust, no brown goo, no signs of any leakage.
I re-bedded much of our 2005 Catalina in 2006 and the vessel already had multiple deck fitting leaks. This was a BRAND NEW BOAT!!! Properly installed butyl tape, in my humble opinion, is a far superior deck sealant than any of the polysulfides or polyurethanes currently marketed.
Though with any of them, butyl, polysulfide or polyurethane they will all work very, very well IF properly installed. IF PROPERLY INSTALLED being the key words.
All deck hardware will eventually need re-bedding, no matter how good your sealant is. Why make things more difficult than they have to be in the future by using Satan's Glue (AKA 5200) that can have as much as a 700 PSI bond strength? Why do this when a product with just 10-20 PSI will achieve the same, and often better, results or outcomes.
It is good to keep in mind that 5200 can actually bond to the gelcoat more strongly than the gelcoat is bonded to the fiberglass substrate. Unnecessary bond strength? Absolutely! The Satan's Glue marketing mavens at 3M have probably driven millions of dollars in repair revenue for boat yards. They have actually spawned & supported an entire business dedicated to selling polyurethane/ 3M 5200 removal products! Again, this is absolutely ridiculous. This level of adhesion for THROUGH BOLTED deck hardware is 100% unnecessary.