currently working on updating the lighting in my trailer, I live in it full time and am preparing to go ff grid, so these will be eventually powered off of a pretty large sized 3.4V battery. each one takes 6 COB mounted star leds. which puts them at around 13.86W per assembly. they are attached with 3mm screws, i just happened to have a bunch of old computer case screws around but lowes sells 3mm x 5 mm which is about what you would need. i picked up the leds for a song something like 5$usd with the heatsinks for 50 pcs.
Update: 8/11/17 6:03am
Ok, I added a bunc more pictures to hopefully help explain why this design has so many holes in it... lol.
the holes in the side are to allow for routing of the wire, in my camper there is only so many places you would want a wire to go. I ended up printing 5 of these, one for the entry way one for over my printer, 2 for the middle of the room, and one for over the foot of the bed( as the head of the bed will have my later uploaded 4 way spot light like the one over my desk, or i may combine the two things into this thing as a sort of COB lighting suite.) the first middle of the room light works as a hub to send the wires out to the entryway light, the printer light, and the main lights. there are 4 holes in the dish on each side where the wire inlet/outlet holes are, this is so you can tack down the wire ends. I have used 4 conductor low voltage (telephone/alarm) wire, each conductor is rated at 7A, the red wire is used to power ALL the leds, the Black wire is used to Ground the entry way light, the green is used to ground the printer light, and the yellow grounds the rest of the main lights. 4 circuits in 1 cable. the picture of all of the lights is labeled to show the wire combination for each light (RY:Red/Yellow RB:Red/Black RG:Red/Green) the main hub light is the most crowded as far as wiring goes, it took a bit of effort to get all of the wires out of the way of the leds. I still need to design and print some sort of cable clam to secure the wire to the ceiling. i will probably do that next. The LEDs are connected in parallel using Bus wire, commonly bus wire is used for solar panels but i find that it is very handy for things like this as it is a flat wire that is pre tinned, which makes soldering a breeze, it took me an hour to solder all the leds together in their respective dishes, in contrast to the 2 hours it took to assemble them with the hold down screws, and orienting the leds so that they would not be shorted by the hold down screws, and further contrast to the 3.5 hours it took to mount them to the ceiling and wire them up. The center hole is a singular mounting hole so that you can attach them to the ceiling, because they are thin and my screws are long i had to use 6 4mm flat washers to move the housings off direct contact with the ceiling. the next thing on my to do list is to come up with a cover lens for them as even accidental eye contact leaves you with polka-dots in the eyes. All in all the light that comes off of them makes you feel like you are in a spiffy new model home. I am very happy with the results. i will update when the lenses are done. :)