.i think the boo over powered the Osage.
could well be if there was too much boo on the back.
As for osage having exceptional tension/back qualities, consider the extra care taken when removing the early growth from the back to insure only the best latewood serves as the back.
My guess is that if laminating osage to a more dense bellywood, you might be pushing the limits of back strain/stress.
an osage bow with a less boo on the back might be the way to go. If you could take some pics of that bow you mentioned, showing the thickness of the boo on the back, maybe someone could offer an opinion about how much boo is the "right" amount of boo.