I have had the seat off of my Tri-Glide a number of times and that pesky little bolt that holds the back of the seat down is not easy to get too, especially if the top box is installed. I have dropped the bolt several times onto the frame, and luckily it did not drop down inside the frame somewhere. And to reinstall the bolt I have had to use painters tape wrapped around the screw and the screwdriver to get it back down into the hole.
So I decided there must be a better way. I ordered a Zinc-Plated Brass Male-Female Threaded Hex standoff, with a 1/2" diameter hex that is 1 1/2" long with 1/4"-20 thread from Mcmaster Carr part# 92700A198. They are not cheap at $10.33 each and an additional $6.00 for shipping, but IMO worth it.
I put a 1/4"-20 hex button head with RED Loctite into the stand off, or you could use the stock bolt. But now it is real easy to pull the bolt out once loosened and real easy to finger tighten it back up to reinstall the seat, and it is still below the deck.