12mm hose in a 1/2" push-in fitting?
 

Strictly speaking, I guess that 1/2" would end up as 12.5mm approx.

My "problem" is that I have come across some very nice hose, and some very nice fittings, all in 12mm, which I'd like to apply to my radiator and pump as well as my VGA cooler. However, my Swiftech block doesn't really look like the type of component which will allow me to swap the fittings on it.

So my question is simply: Using push-in fittings, would you consider 12mm hose in a 1/2" push-in fitting a good enough fit? Or a recipe for disaster?

if you mean the swiftech push in fittings
http://www.swiftnets.com/products/mcw20.asp
than they are for 1/2" OD (3/8" ID) so i think they won't fit...