One more thing on the topic of fins, the more I looked at the fins, something else seemed different. I tried capturing this in a photo but could not get the photo quality to really show what I saw ( I will keep trying though), the fins are split between the tubes. I have never noticed if this is the same on other radiators optimized for low speed fans. I will have to look closer next time I have a low speed fan optimized radiator in my hands.
Do you mean the fin wasn't solid for the whole depth of the rad, but had slits in it? My MCR320 is like that.