criom, like PC, I think ducting a/c over the lights is overkill. I think you'll keep the surface of the cooltube very cool compared to op airmass temp just by pumping ambient temp air through the tube (unless it's summer and you live in Las Vegas ).

That's your goal, BTW- stopping transfer of heat from the lamp to the room airmass. Cooling the surfaces exposed to the op airmass is how this is accomplished.

You won't stop the radiated shortwave IR with a cooltube- your hand will still feel warm in direct light- but you will stop the longwave IR that normally heats your op airmass.

Reserve drawing air from the a/c as a last ditch trick if the cooltubes don't get your room temps down to the necessary 80F max- but don't put it on the lights, put it on the plants.