Brad,
My 440 cracked the 2 middle bores just off center of the thrust. 4.350 bore, tall fill. Pic below.

If you remember, this engine saw heavy loads of nitrous occasionally. So occasionally that I sometimes lost track of my tune-up! Thought I was on 175 1st stage, then 225 2nd stage. Nope, I had 250 in the first hit, because I had agreed to race a guy on one stage, 3 or 4 months earlier. I was on marginal fuel for that much spray, so things got unhappy about 1000 ft. out. I sleeved those 2 holes and replaced those 2 pistons and continued to run it.