im gonna have to agree with OM here...
in a 4'x4' space you could fit at least 20 plants if theyre in 1.5 gallon square containers (currently what im doing...link in sig)...theres no need to go vertical, you can accomplish just as much and possibly more with a flat set up.
IMO, vert set ups are optimal for high wattage, high plant number grows with (possibly) limited space...they work because of an increased number of smaller plants under maximum power...FloJo's grow is a perfect example of a vertical grow
and how would it not gain anythong over a flat garden? itd fit 3-4 times more plants under the same light.
..just because you add more plants and angle them to grow towards the center doesnt necessarily mean youre gonna get a better yield...youre still using the same amount of light so your increase in plants would probably just mean a decrease in yield/plant
in a 4'x4' grow area with 1x600W youre sitting at 37.5W/sq. ft....on top of that add the previously stated fact that the lumen output will be decreased due to the subtraction of a reflector (lights going everywhere instead of concentrated somewhere)...basically, youre gonna be putting MORE PLANTS under LESS LIGHT
if you cut your number down to 28 (at the very very very most), confined your space even more (since youre only using 1x600W), and just rooted your clones for a week, no veg time, straight to flower and lollipopping the plants this may work (maybe), but youll never pull 2 lbs. from it (i think you said that somewhere)...2 lbs would be 1.5g/W and you'd have to average 32g per plant...
but for whatever its worth (which probably isnt much), when going vert, go big or go home or its not worth it
my $0.04