as for stress, there's realy no mathematical equation or anything, but continual abuse is a true ticket to herms. being that you have not started flowering yet, you should be ok, if you can get the temps down. the cool tube will help by about ten degrees, imo, and will have you at almost ideal.

as for the flowering, the hps will not do you wrong; compared to cfl's, it's like comparing a finger to a fist; biiiiig difference.

and as for the prestretch, it may actually help you; you see, bb is not yeild restricted meaning the top cola's will be comparaitve to a single cola of an untopped plant. with this nature, the side buds grow nicely as well if they get adequate light. the stretch will put less foliage in the way of the lower sites, increasing your overall yeild. dont be surprised if you don't get rock hard density out of them; mine are rather fluffy and stretched, even under a 1000w.

hope this helps.