Why don't you ask your friend what he thinks is the advantage of vegging under the hps? Then, when he tells you because the light spectrum is better, tell him he doesn't know what he is talking about because he can get a better vegging light spectrum from cool white cfls and the plants will veg better under cool white cfls.

There's only one way to tell if your ventilation will work - try it out! Now, so you can make any changes.

PC :smokin: