Oh, it would sure be nice to some day inspect these bows! You lucky englishmen...
Have you made any of these X1-3 style bows?
I'm actually surprised they held together, since 30" draw out of 66" bow is quite a lot at 100+ pounds. Maybe with heat treating those bows wouldn't even have developed chrysals...
High crowned back actually effectively does the same thing as heat treating. In my one elm bow i had high crown back, pin knots and heat treating - i think you guess what was the outcome.
Some people heat treat all of their bows and it sure is effective with elm if the material is knot free, but many cases this is not true. I've broken couple of warbows with heat treating when they were already ready.
Anyway, my elm bows have been 72" and i'm planning to do some 75-77" bows, under 70" is just too short to be safe. Maybe if i chose the deflex side of the stave, but.... that's not my habit of making bows!