DrWizard:
I'm not doing a fancy current-limiting circuit, but I do need current limiting resistors. These 10W chips draw a lot of current, so I'm using 2 watt resistors. I had initially planned to use the ceramic kind, but for price anavailability reasons ended up with the big wire-wound kindd . The whole floodlight is in an aluminum housing with fins. The LED chip is mounted and heatsunk at the middle of the back.
It would be good to see pictures and a hand drawn circuit.
I would suggest that the current limiting resistors are mounted outside the unit.
I have done similar using 96 IR LED in the past inside a floodlight housing, the limiting resistors heated the housing so much the LED's blew.
Do not know much about the current 10 W designs.
Have you measured the internal temp of the housing in origional configuration ?
DrWizard:
I hacked 4 of these 10watt RGB floods as described 3 years ago, and they survived 2 whole seasons of a Christmas light show so far without problems. Now I am hacking 5 more.
It was the heat that got me.