Looks like a great core, with a nice, low pressure drop.
Boiling the tubing works really well too. I have used it to get 3/8" braided silicone(very stiff!) over a 1/2" barb. When the tubing cools, it makes a contracts to make a watertight seal over the barb; almost no need for hoseclamps. Only trouble is trying to get the hose *off*. I had to use a utility knife to cut mine off.
Still, getting 1/2" over 3/4" tubing might be tough... 1/4" is a lot of stretching! If you do use the heat gun, be careful not to weaken the tubing too much... would suck to have your tubing split when your comp is on! Anyway, I'm sure you know what you're doing tho.
