I I was going to mention just doing that in my other post but they really didn't design it for that and there's an awfully large pushrod galley that doesn't need to be so big so they would have had more metal between the cylinder and the opening but you could certainly put something there with the metal that you do have and it would help the issue.Funny you should mention that about putting the bolt in the middle. I finally got tired of replacing head gaskets and a flywheel that cracked off a piece at the keyway and replaced it with a JD labelled engine, just so I could sell it. A few weeks after it left for it's new home I went to visit a friend, who had just purchased the same model tractor. Within a few months he had similar issues. Being an even more stubborn person than myself, he drilled & tapped a hole in the block and a clearance hole in the head for either a .190 or .250 bolt (Inco718, of course). That actually fixed the problem for several years.
Has myself and others have stated though this should not be a recurring problem. I have never had one fail a second time and I don't even always mill the heads down on a flat surface..
I have done many of these by just scraping off the head and getting it nice and clean and not even putting a straight edge on it to see if it's warped at all!
I simply clean the head and the block up thoroughly and put the new Briggs & Stratton gasket on there as I have never used an aftermarket gasket even though I think there's a potential they could be better than the factory one and I torque it now with the new tightening pattern and the 250 inch pounds procedure but I used to do these with the old torque sequence and the 220 or 225 or whatever it was and I still never had any failures back then either.
So while it is an epidemic problem, once I put a new gasket on there it's not been an epidemic problem in the future at all.
However, if I were having repeated failures I would certainly take extra steps and if milling the head flat and permatex spray gasket didn't solve the problem I would be drilling a hole and tapping some bolt threads!!