I would assume that the fan assembly doesn't block flow around the fan? If so, then the fan shroud is really not doing anything except blocking any air flow that could possibly pass through the radiator outside the fan diameter.
Yup. That's the problem. Although the fan assembly doesn't totally block the air coming through the radiator outside of it's diameter, it restricts it almost completely. :BangHead: I had tunnel vision when I made the darn thing and only concentrated on getting it all to fit together and look good. I had so many aspects of the car build coming together at the same time that I didn't notice the potential monster problem I was creating.
I'm not going to try a 50/50 mix in the system because I'm committed to keeping the Evans coolant. - But I am curious to know if I would have been overheating running regular antifreeze. If it weren't such a pain in the butt to switch back & forth, I'd give it a try before making any modifications.