My idea: I attached my leds to a plate of aluminium, on the other side of that plate i put a lot of computer heatssinks and fans.
I guess the disadvantage of this is that i have 2 layers of heat conducting paste instead of 1, when attaching directly to heatsinks. But idk if this really matters.
On the other hand the L shaped plate allows me to easily mount it to the ceiling with hooks and chains.
Ill be adding 4 more bigger heatsinks in the corners.
For these (a total of 8 heatskinks little bigger as the black one in the middle) + those in the picture i payed together about 15$ on ebay including shipping.