I found some huge rawhide dog chews at "Pets at Home". One gives plenty for backing the bow with a continuous piece for each limb. I soaked the dog chew in the rain water butt overnight and unwrapped it this morning, it's pretty slimy messy stuff even after washing in sodium hydroxide (caustic soda) solution and thoroughly rinsing.
It's tough stuff and it needed tin snips to cut it. I've done the patched limb, I'll give that a few days to dry out before doing the other. I use a small deep fat fryer to melt the glue. It's spot calibrated at 70 degrees C and does a great job.
See also this post:-
The glue tend to gel a bit on the cold surface of the bow, but a quick application of more hot glue with a paintbrush helps keep it good and liquid.
It's the combination of water and heat that liquefies the glue so it takes a good time to fully harden/dry. The string binding holds it firmly in place whilst allowing the moisture to dry out, it also leaves a funky ridged surface. A waft with a hot air gun also helps to ensure the glue is liquid under the rawhide.
Hopefully I may end up with a working bow, it seems like a vast amount of work to plough into the bow, but I enjoy the challenge and if it survives, the end result will be something a little bit out of the ordinary.
I expect any of you who are my age are singing "Rawhide" in your heads now!