How about a hard-fill? I'm not sure how you could isolate it to just that spot though. Hard-fill is what a lot of builders do to make the block stronger and to resist deflection. It's basically a concrete-like iron mix that you pour into the water jackets and let harden up. It doesn't allow the cylinders to deflect at all. Most of the cooling in your engine takes place in the cylinder head. Having coolant flowing through the head is a must.