From .030 to .040 is a .010 difference. I know you knew that already but bear with me. Maybe you didn't think of it like this. Another .010 is "only" .005" from half bore. .005 difference in the radius. Got that part? Now, if a .005 difference in the radius of the bore on a block was "too much" and made the block "weak" as you're eluding to, then that block needs to go in the garbage if it ever needs a .030 over bore. Stop and think about what you're saying. You're saying that 5/1000 of ONE INCH is the breaking point.
