I bought a 2 ft fixture that uses these 2 t5 ho bulbs....it's a 10,000 lumens setup.
The bulbs are different....it's like there are 2 tubes that constitute 1 bulb so technically it's 4 tubes.
I was looking at it and there isn't much to it.....a ballast, 2 bulb connectors, and 2 rear bulb retainers which the part numbers are on just about everything.
It looks like the fixture is large enough to accommodate an upgrade to 8 tubes and all I would need(that I already have) hardware wise is a drill and tap kit really with a few bolts, nuts and screws.
Only complication I see would be the need for active cooling..I think a couple 45-90mm fans would do the trick but I would need to cut holes for them(hole saw bits..np there) which isn't too big of a deal and an ac/dc adapter which i guess would have to use an external brick since there wouldn't be any room inside the fixture after doubling the amount of equipment housed in it.
At some point I may do a cost analysis to determine how much it would cost me to upgrade it. Reason i would want to upgrade it vs buying another fixture is all the other 8 tube ones are much wider and I want a compact design.
Other than that I suppose I would have to raise it up a little height-wise so it will not melt the plexi-glass top. lol.
How would the plants tolerate it? lowland neps going from 10k lumens to 20k?
p.s. off the top of my head....bulbs would be $40, ac/dc brick $10, 2 dc fans $10 for high flow ones. guess it depends on the ballast and the connectors.