When I was first fiddling around, I made a Poplar backing and put it on an Ipe core to test out how a wrong combination would work. I kid you not. I got it to full tiller, but after about 5 shots, of course, the poplar pulled a splinter. I proceeded to superglue it down and put a paper grocery bag backing down, and low and behold, it's still shooting now, a year and a half later!
So I would have to say that it is a pretty strong backing.