Again, I really appreciate yall's thoughts!
adb, I never suspected the hickory back failed first instead of the jatoba belly on bow 1. All but one of the backing and bend test failures I've had with hickory have been splintering type failures- they looked kinda like those the single small hickory splinter on bow 2- which was ripped from hickory board as bow 1.
Some better pics of the bow 1 break in hopes that other folks will weigh in:
None of the glue lines failed. A good bit of the maple core is still intact and it's splintering on one side of the break is definitely due to tension. Maybe that points to where the failure started?
toomanyknots, I sure want to think the thinness of the belly lams had something to do with the breaks but I can't rationally come up with a reason for that conjecture/hope.
c.d.