I have seen a few cracked blocks lately on cars running e85, seems the cylinder pressure just splits the bore from bottom to top. It's totally up to your tuner, and how much timing he decides to run, I hope he is good because you can't see massive cylinder pressure, and you can't know when it is too much for your block to handle.
My suggestion is to keep the bore thick, not oversize the pistons. Or perhaps sleeve the block...any strength there will help.