How close, is to close for rad fans to water pump pulley space

I had a very similar set up with 10" fans, but they drew a lot more air, I believe it was close to 1800cfm each.. I overheated because the shroud did not allow enough air to move through the radiator. I was going to cut more holes in the shroud but ended up going back to the factory fan, shorter clutch, and bought a factory shroud. Cools great now, not to mention the fans where noisy and never came off of high because it just couldnt move the air to cool it