Re: Fibreglass deck getting soft
If your foredeck is solid glass then the ply may be backing plates for attachments on deck.
If you do decide to stiffen the area I would suggest you use an epoxy resin, it will cost more per litre but you will use less and finish with a stronger and lighter job.
A suitable stiffener should be added to the underside, but only after you check the support at the back of the anchor locker has not been damaged or broken, or rotted.
As for bending glass around corners, don't try to bend it too soon, let the resin break down the bonding agent in the glass first and will lay around a curve without problems; just put a radius on external corners and a fillet on internals, the latter will also make it easy to paint and keep clean. Use only glass designed for use with epoxy, not chopped strand mat or you will use too much resin and end up with a weak and heavy job.
fairing can be done with a mix of Microballoons or spheres mixed with epoxy to a about toothpaste thickness, apply a layer of resin, let it go tacky and apply the filler, let it cure overnight, sanding is very easy.
Any glassed or filled areas must be painted to prevent UV damage, this applies to epoxy and standard wax resins.
Growing old is unavoidable. However, growing up is still optional.