hi RickF
Have you thought of superglue - Ive used superglue on several occasions to glue, plasticard to GRP coated hulls.Up to today, none of the plates have come off - however, after I have finished plating the hull, I give the plating several coats of undercoat first to seal every joint - normally with the Humbrol paint lightly rubbed back and then finished coat of the chosen colour. I prefer to use Humbrol or White Ensign paints - then, overspray with satin varnish, again, from Humbrol. This seals the hull well - UPTODAY IT HAS - and one of the hulls has been knocking around for 12-14 years.
The only problems with using superglue in such a vast quantity over an area is it must be done in a really well ventilated room - make sure it is ventilated - just as an afterthought sometimes if you use too much superglue it attacks the plasticard & it gives the appearance of rust (well it has on mine) like a fine crinkly surface which, depending on the hull you are building adds to the character.
Hope this is of some use.
Aye
John E
BLUEBIRD