Looking for a 16oz yield from two plants. Any possible advice is greatly appreciated

Enjoy the ride. Don't add up results until in the jars.
Looks good but ya gotta bring it in.
It is only this time. When you are looking over a sea of jars it will all seem so unimportant.

 

4oz per plant is a healthy estimate for a single plant under a 600hps light. 3+ oz is my average growing 12 plants under 3 hps lights. i have broke 4 oz many times but i have got several 2.5 oz plants too. it just depends on the strain and the climate too. if you have excessive heat issues it will cost you in your final yield. hopefully you will avoid heat issues with your cooled reflector. experience is another huge factor. if this is your first or second grow, chances are you will not get a half pound plant. i have been growing indoor for 10yrs under 600hps and i have never had a 8oz plant. i have come close but that was one of my best grows. you do have a advantage over me by vegging longer and topping more. i only veg for 35 to 40 days, topping once. my technique is for a faster turn-over and shorter veg time. i grow in 3 gallon containers due to the fact my plants life cycle is 3.5 months or less. also, many growers are claiming bigger yields with the high quality LED lights but i have not tried them myself. you could always consider getting a very high quality LED light if you have your heart set on a pound harvest from 2 plants. just my two cents!

 

My largest single plant is 15oz's in a 7 gallon smart pot of promix with GH nutrients under a 515 watt platinum p900 mostly.

I've had a few over 10oz's. I'm definitely going to do over that with the plant I'm harvesting in the next few days. It's a monster.

A lot depends on growing method. It's not all about the lights. Hydro will definitely get you higher yields. I have seen a single plant yield a pound here on GC with a 600hps in a 3x3.

 

Strain is also very important. I've never got over 6oz's with a few of the strains I've grown. It's usually only a few that get those high yields. Veg as long as possible and flower when you think you may run out of room, then cut it back to fit in the space just right. Large plants=large yields.

 

16oz from a 600w HPS is very possible, if everything is perfect you could get 21oz from one cycle.!

a 5' wide box is almost too wide for a 600w, maybe try a coliseum trellis to get the branches on the sides closer to the bulb....????

the closer the bulb is to the plant the more it will produce,
keep the tops 12-18" from the bulb and the canopy 36" thick,
with temps, ferts, RH, pH correct, this will maximize plant growth.!!

 

Good call on the 5 feet. I just noticed that. You'd almost be better off making the room smaller so you have proper distance to reflective material. This could increase your bloom light's par reading in the flower room by 10% or more.

IMO the perfect size footprint for a 600 watt hps is 3.5 x 3.5 or maybe 3x4. They're a little small for a 4x4. The single plant pound I saw was from a 3x3 tent. That way all of your plant is right in the focused footprint of the light instead of stuff out to the edges of the 5 foot area not getting good coverage.

Cooltubes work great but they reduce the light footprint a lot compared to open bulb hoods.