I will never use 4000 uv. I used it twice and it made it less that 2 years both times. Once on my 2005 Sea Pro, and once on the gunwale seam on my 2320. Use 5200. If it was an outboard, that's one thing, but you are talking about 4 small pads. Just because it is made for permanent applications doesn't MAKE the applications permanent. Do it right, once. The sealant won't see UV, but you want the sealant to be part of the mounting system, and you want maximum strength with sealing. If you ever want to take it off, just apply debond and use plastic putty knives and a little patience. Do use the red labeled Fast Cure. 4200 at least. Use a little extra so it just squishes out, the clean with a rag dampened with mineral spirits.
The guys that hate it on here remove old stuff/replace with new for a living, and I understand that too. Parker uses it at the hull to gunwale joint, and a swim platform is no less permanent than that.