I don't for sure. But as long as there is steam coming out of the ends, then it shouldn't burn. It's not a sealed container to make the pressure rose any appreciable amount. So the water that's in direct contact with the wood should be boiling temperature, with the steam being a bit above that. So as long as the paper towels stay wet, the wood won't burn. I've done this a few times with good luck. I can put the heat gun almost on the foil for 30-40 minutes and not burn the wood underneath. If you remove the foil and towel while it's still hot, the towel will dry almost immediately from steaming.
I'll find out this evening if the steaming and bending held. I was able to move the tips a little under 1/2". So between that and the handle moving a little, ye string will hopefully line up with the handle. It should be close enough I can fine tune with the nocks. I left the tips about 7/8" wide.
Kyle