Changing to HID lights in 12/12 ?

I will have a new 600 watt HPS setup next week. I am currently almost 4 weeks into 12/12 with a big sativa.
My plant is doing well and flowering pretty good under t5. This is my 1st grow and I have made my share of mistakes. I am trying not to make any more.

Should I attempt to change to the HPS at this stage of flowering or just leave it alone? I am using 550 watts of T5 right now, so while I am not grossly underlighting, more certainly couldn't hurt.
I realize that I can't just plug this HPS light in and go without getting enough ventilation to avoid high temps. I intend on having appropriate ventilation and suspect I still have another 2.5 mths to go on this sativa before she's ready- I would like to get the benefits of the HID if it won't do more harm than good.
I just don't know if the extra lumens will cause a stress issue that I don't currently have.
I threw out another post and received many recommendations about properly venting my space. The only question I didn't get any feedback on was the one I am now asking.

Opinions?

Go for it. Nothing wrong with what you suggest as long as you stay on top of potential heat issues. HPS > T5.

T5s grow corals that are much, much, much more light sensitive than mj plants. If you have a fully wrapped mylar room/box my guess is that t5 would actually be better for overall growth since it is not point source like hps/hid so you will have more even coverage. The mj boards are full of teenage potheads, the reef boards are full of doctors and engineers. Lumens mean absolutely nothing to plants, par is the only meaningful measure of light effectiveness for plant growth, and it is well established in the reefing community that t5 is as effective as mh. No one uses low k lights over a reef so i have never seen a par comparison between hps and 2300k t5.. But at 14 and 20k there is little difference.

I did the very thing your asking. My crop was 4 weeks into flowering under CFLs. I threw them under a 400 watt HPS. I just kept the light a little higher then normal to let the plants get used to the new stronger light. I lowered it over a couple of days. No problems so far. Just have to keep the temps down and you'll be ok.