another 360/408 over heating

Every overheating issue I read about, concerns using electric fans. (IMHO..I do not think they draw enough air flow through rad to cool efficiently)
Most cure the problem by:
- going back to the factory fan (or a similar fan...maybe a bit bigger)
- a properly fitted and sealed fan shroud <most likely a stock replacement> (by properly fitted, it is sealed so air is not drawn between shroud and radiator)

The sole purpose of your fan is to draw air THROUGH the radiator to cool the coolant as it makes it way through rad.....if you have air leaks around shroud, you are hindering this process by making the fan inefficient at it trying to do its job.......drawing air from around rad, instead of through it.

I think by drilling those extra holes in shroud, you are causing another inefficient "air leak" for fan to draw air from.