I've built a mockup of my Va'a Motu's forward crossbeam and am using 1/8" (3mm) plywood in place of the stainless steel plate I will use on the real hinge.
I drew a careful line where the beam will be cut and glued on two 1/8" plywood spacers that allow the hinge parts to slide past each other.
The 1/8" ply pieces that you see will be stainless steel plate and the fiberglass pins will be 5/16" stainless. I drilled pilot holes for the fasteners to make sure that the beam stays straight when it is reassembled.
I cut the beam in half with a thin kerf pull saw.
A bulkhead and side blocking to a depth of 4" (100mm) are glued into the cut ends of the beam to reinforce it.