Thanks for response all.
As indicated by Bill, I am using sheer clamps in the hard to get at places and for a couple of other reasons.
I stripped the deck quite a few years ago and I ran each strip over the edge so no sheer strips on deck. When I removed staples there was some springback so the deck has to be pulled down a bit over the bulkheads like a ply deck. the bulkheads will be temporarily held in place as I haven't decided whether or not I will use them.
I don't intend to add deck hatches & I'm a fairly big unit with most of my size in the upper torso rather than providing shade for my wedding tackle, so I have access issues with the standard taping technique.

Back to the topic of suitability of using ply for sheer clamps. I made up some ply sheer clamps to determine for myself there suitability and yes They would do the job and yes they would be more difficult to shape nicely with a plane. so will scratch the idea. However, i have found a big chunk of JELATONG in the workshop. We use it for carving, it is light with straight grain. If it is suitable for use with epoxy my problem is solved. initial reserach into Jelatong is that it contains traces of latex so may not like epoxy.

cheers all.