I just had to try my hand and an LED array after being out of the hobby for a short time and just recently jumping back in. I don't have a PAR meter, so my lighting choices were made solely based on other threads from this site that were using the same tank or a tank with similar dimensions.
x4 Cree XP-G Cool White
x1 350 ma moonlight driver
x1 12 in heatsink
x4 Thermal Sticky pads
I saw a similar enclosure on here and that was my inspiration for how to build mine. I did it was parts from Lowes and just a few hours to put it all togeather if that long.
You can almost see I drilled holes in the top of the heatsink, looped cable though and secured it and had that ran though the suspension cables. This way the suspension cables are actually holding up the heatsink, with the enclosure resting on top of it.
You can see in the last picture, I used something called a "closet flange spacer" I found in the plumbing department to make the curve. I just cut the flange in half, drilled holes for the sheet steel and started bolting it down. By using the flange, I got a fairly nice curve that was consistent out of the metal.
After that it was just a mater of figuring out where to put my driver (will be moved externally before long) and how to run my suspension cables.
The hardest part for me was that I wanted that smooth curved look, but didn't know how in the world to accomplish it. That's where that flange became so important in what I wanted to do.
So far I love the light. I do think I messed up by not ordering optics when I got my LED gear, so that's something I'm going to go back and do. I also plan on adding some DC plugs so I can easily move the driver out of the enclosure and make everything easier to take apart if I need too. I've also went back and covered it in a metallic contact paper material. Sure beats polishing the steel to get that shine.
Total cost for this was $76.06. $48 was from rapidled, and the rest went to the enclosure.
I'm not to good at these 'how to' threads, so if anyone has any questions please ask and I'll do my best to answer.