Just stumbled upon this post today....heres my constructive opinion..
First off that mylar since it isn't tacked up flat against the wall is going to be moving and bending when the fan blows which will cause HotSpots. (high concentration of light at different points, not a big worry.)
Also your running 4 1000watt lights which seems like no ducting for aircooling to exhaust your air out and I do believe California stays pretty warm. You should exhaust the air out or if not exhaust atleast have it setup to if it does get warmer..
Plus you do NOT want to go soil if your running 60 Plants. The reason I think so is because for one..
Your going to have to discard 60 pots worth of soil somewhere..
Your going to have to water those by hand which is going to be way to time consuming..(2minutes spent watering and plucking dead leaves, rotating plants etc... will equal 120 minutes or 2hrs almost everyday dedicated just to watering!! Toooo much work. this can be automated.)
Also your going to have to bring in enough bags of soil to fill up the pots..calculated its gonna take alot of bags plus it'll cost some money (dont know if you have a budget.)
And plenty more reason I'd rather not continue on...
Go HYDRO... Raise that tray up enough to fit a reservoir underneath it.. with that size tray and amount of Pots that'll soak up nutrients using Ebb and Flow method would just take way to much water to hold in your reservoir to be economical.
I would go with a Top Feed method with a Fish Pump from your reservoir to a mainline that has smaller lines out to each individual Pot..This way you could use a smaller reservoir cause nutrients will be recycled back to the reservoir. (Very easy to put together it'll take you less than an hour, and fairly cheap.)
Also if your thinking of Sea of Green Do take in considering that Yeah you'll pump out more...but you'll get it a little at a time...Also you'll end up being a slave in your own growroom cause it'll take alot of little jobs everyday to keep the cycle going. (cloning, vegging, transplanting, making different nutes for each thing, so on and so on I think anyone who has done it agrees it is tedious and can be time consuming where daily attention is important.)
If your going for the long haul like thinking your going to keep that grow room of yours for a year or so more than go for it. But if not, I'd suggest doing a few "big" crops.
Also I don't think you'll need to do 60 plants, thats alot.. I had a setup simliar to yours with 28plants and 4 1000watts and yielded 8 lbs dried bud. So your 6lb goal is WAY attainable.
Also dunno if Electricity is an issue but do consider that if you keep a veg room you'll use lets say
1000watt plus for lights and fans in veg room.
4000watts for lights
1000watts for random fans, pumps, dehumidifier, and whatever else..little things add up..
Thats over 6000watts plus whatever you use to live on in your house..Thats gonna be alot of juice your using so you might as well cut it down unless its not an issue..
You said you have Both bulbs MH and HPS, are those switchable ballasts? you can veg in the same room and them flip the lights and flower in there too that'll save you space but will be an excess of electricity..since plants are small you can veg all your plants under 1000watts then put them in there and flower it'll save you from wasting electricity...actually even a 600watt MH will pump out enough light to veg all your plants.. considering your going for small plants.. maybe (12-15inches in veg max i'm guessing)
Also looks like you have a flat ceiling you could of gone with a Light Mover and even got more plants or made more use of your space in there.
My advice grow lets say 40 plants veg them to about 20inches then flower and space them out you'll end up getting the same as if you did 60plants.
Do Hydro, put your pumps and everything on a timer so it'll water it when your not around..spend your free time doing something else...like getting stoned...haha.
Definitely get atleast a 125lb Charcoal Filter and Slap that in there to kill the smell a garage is not so insulated and smell WILL leak out and thats a security breach.
hmmm...can't think of anything else right now.. but I am sure I will.. Sorry for the long post looks like your trying to go for the gold so maybe this will help you out.
P.S. That room has Potential...