Just think what it could have been if you used something that is made to line your walls and not something you cook french fries on. Plant looks good, but I can guarantee it would have looked better without the aluminum foil. Your next grow try out something else and see if your results are better, I can already tell you the conclusion you will reach. I wouldn't listen to that tea tree guy, he also thinks that CFL's are better than a 400 watt HPS using his charts and graphs and shit.
You're talking about
https://www.rollitup.org/cfl-growing/161775-220w-cfl-4x4-floor-plan.html ?
That's based on a plethora of CFL growers who report higher gram/total watts(kwh) compared to HID. Search, you'll find them. Not everyone is honest, mind you. The honest answers share a trend, though. But there are so many other factors also involved.
It's also based on the concept of a maximum of 16 plants(and a large unused closet). It's for small time growers that won't need 400W of power. Maximizing yield through the number of plants is the key to all commercial farming success. That's what the set-up does for the average joe. It grows a lot of plants with very little energy.
It's also a concept to help people understand there are better ways to do some things. Like in-canopy/side lighting, instead of using excessive amounts of reflectors, which probably aren't ideally used anyway(like applying them to flat walls, the angles suck, waste of time IMO). You want the reflectors at specific locations and angles for them to be truly valuable and effective. It could also just cause hot spots when done incorrectly.
I don't think you even understand the concept of foil when used for cooking. It's main purpose, besides making clean-up easy, is blocking radiance(light). It stops food from getting burned on the outside, from intense IR radiance, while staying raw on the inside(baked potatoes, for instance) by evenly distributing heat via it's metallic properties.
Exactly what makes it excellent for cooking it what makes it excellent as a light(radiance) reflector. It's even easy to crumple up, recycle, and start over if you fuck it up.
Out of curiosity... what's backing your guarantee? You seem to have the growing experience of a typical forum lurker.