Stealth Wall w/ door grow room: 13.5xft length x 3.5ft width and 8ft tall...

...With 3 600W HPS lights w/ cooling tubes.

The lights are spaced equally in 3/4 of the room. about 3.5x 3.5 space for each light. The remainder of the space is for entry and a small shelve that will be built for supplies, ballast ect.

My idea is to grow 3 plants in 5 gallon buckets under each light. One plant per light. The strand is LSD, a sativa- indica hybrid. I want to maximize yield potential for my room and to do this would be to grow thick 5ft tall x 3 ft wide tree bushes.

Any tips, suggestions, training methods for my purpose be would be much appreciated

More gallons per bucket, go with 7 gallon containers if you can, and you will need more plants than one under each light. If you are looking for 5ft tall 3ft wide bushes indoors, you will need at least 10 gallon containers, even then plants have limiting factors indoors. Venting will be key in your room, do you have intake and output set up? There should be a low pressure pocket in the grow space, do this by making the outtake fan a little more powerful than your intake. Also make sure to have powerful fans, you could do a nugbucket type set up and have fans in between the plants blowing upwards for maximum gas exchange. Reflectivity is huge, if the room is white that will do, but think about investing in the diamond foil type reflective mylar, it uses aluminum shavings to boost the far red and infrared reflectivity levels to 98% (28% better than white) which is key in changing phytochrome pfr into pr and helping your plant develop during flowering.

For large production simply look at one of the many, many, many, many medical growers on this site. In Subcool's old school organics, there is a thread by nugbuckets on his "mainlining" technique. It's not unheard of advice, but it's put together in a comprehensible way and will give you the best understanding of how to encourage the biggest blooms you can get.

Did you know you posted this in the LED and other lighting forum? Most of us used to grow HID so you can get advice here, but since you decided to post here I will give you additional advice. If you can make sure to buy Dual-arc HID bulbs; sometimes referred to as ceramic metal halides. They contain a MH and HPS in a single bulb. If you were to install this and run some pure red leds as supplemental light it would lead to amazing results. This is the type of set up that I'm making for my friend, and if I were in it for the money I would probably run the 3x600 watt dual-arcs, with 4x50 watt 2:1 660:3000k set up around the lights to boost the flowering end of the spectrum for the lowest wattage possible. That's what I would do. Then again I'm an LED junkie and any hype I build about LEDs should be taken with a grain of salt.

Keep on growing,
ILovePlants

thanks for the advice buddy.