dave wrote:

Lew

the decks are solid glass and the headliner panel has been removed
so i could remove the deck hardware

The easiest way to stiffen the side decks based on your description
would be to loose fit a piece of foam, say 3/4" Divinycell, to the
underside of the deck, then remove it and glass all exposed foam
surfaces with a couple of layers of 10 oz cloth.

After it cures, install it using some 5200 adhesive.

Allow the 5200 to cure at least a week, then remount all the deck
hardware you had to remove to fit the foam in the first place.

The 5200 will not be as strong as if the foam was glassed directly to
the bottom of the side deck; however, it should be strong enough and it
eliminates trying to lay glass overhead.

Lew