In My opinion option 1 is the only option. I consider 1/3 water to be a plus not a negative. The weight of a plywood bulkhead with no glass on the plywood, just epoxy coated is insignificant compared to the weight of expandable foam fore and aft. And I haven't noticed a problem with stress points in six boats and ten years of paddling/building. In fact I would prefer a bulk head to stiffen the deck behind the cockpit where you sit to prevent flex and stress cracks in the deck. Option 2 seems just plain dumb to me. it's a waste of space, ugly, traps water, and is by no means light weight especially once it traps water. Option 3, why bubble wrap? it's poor solution to float bags. Again ugly, becomes dislodged and is unnecessary garbage to have to carry with you.

In a glass boat use bulkheads in a skin boat use float bags!!! tried and true methods!

Kent