Agree with Uffe. The bigger the better. Word is the ones with the flat tubes cool better because you end up with less "fluid width" so it is easier for fluid in the center of the tube to give off heat.
I ended up bending hard line to run out from the back of the rad. to the front through the gap between that rad. and the core support. The gap is small and there are shap edges so I was a little concerned about rubbing a slice in the line and dumping the fluid as fast as it can pump it out.
Brent