Thanks fellas. The resources avail on this forum are top notch!
Rasped/sanded the backer away. Process of doing that showed there was bit of a ridge running full length.
Also could see that bond was better at clamp locations, and visibly less good immediately next door. And 20 clamps exhausts my inventory.
Second try is now curing.
Made sure core back was flat. Made sure new backing was flat. Laid length of tin on top of backing. Clamped handle area using large surface area clamping blocks with 3 clamps. Used bicycle tubes to tightly wrap from tips to riser.
Now the hard part . . . . waiting!
Thanks, again.