Paul:
It is not a fun project! and I also wish they slapped the evil design person. But that is in the past.
Some tips that help (see other Forum topics)
Drilling out the head and drive them in, to find the spot (if you tape over the ss " for contamination reduction" then a grinder could be faster for knocking off the bolt heads on the outside)
A gear wrench can help in the confined areas (top nuts)
The ones beside (Hopefully not under the bulkhead) may require the cutting of the fiberglass tape that covers them, to allow their removal (one of the osilating tools like Fein multimaster make this a bit less effort)
It is easiest to cut the rub rail and re attach it (Fein tool cutting at a 45deg so that the pc may be re screwed into the sides it was cut from)
_______________\___________________________________
\ \/
\ / \
-----\--------------------/---------------------------------------rub rail / hull side
Reassembling the top nuts can be helped, by adding elec tape (Or heavy grease) to the outside of nut: so it is a very snug fit in the gear wrench.
Best of luck:
Norm
P.s. be cautious not to bust up the ceiling boards they are a pain to remake and match for color and fit. You may want to remove (unscrew) some where you think the nuts are.