I think it's a great idea. Not only for the pressure it places in the middle of 2 ports that only have 2 bolts now but for stability too.

I admire the small block for it's 2 higher studs on the end and small Fords for their staggered bolt pattern. One up, one down etc. BB are all inline.

Where I see that as a minor potential problem is when the engine moves around on it's rubber mounts. The exhaust system is constantly yanking on the header assembly. This may eventually crush the top and bottom of the gasket, leading to a leak.