Your setup will work just fine.... BUT:
Changing the barbs at the innovatec to a 3/8 won't do the trick. You fix the hose issue (as 2 x 3/8 = 1/2) but your problem will be that the innovatec's are internally designed to work with 6.5mm
I'm using a similar setup, but I opened the Innovatec, and it's just one solid plate of copper.
Take a drill or a dremel and make a flow path.
After I did this, it was working just as good (flow wise) as my D-Tec Z chipset block.
(I'm using the innovatec for my GPU, as I'm not OC'ing my Gforce4)