Exactly, if your going to spend the $$ to go big (400+) then darton sleeves would be the real answer, do it right the 1st time around and save later. Any amount of bracing in the coolant passages does not fix the issue. The area at risk would be between the cylinders. This was the issue with the inline six BMW's when pushing the S54 block to 900+...the answer was darton sleeves. With our blocks there is not a whole lot of meat between the slugs. I would like to see where those block are cracking that are mentioned. I bet its down the cylinder walls between the pistons.Those block guards have been around for ages, last I had heard of people using those they were creating cooling issues due to restricting the coolant passages around the cylinder walls. That's been years and years ago, sleeving made that mod obsolete.