Questions before starting my build

[LukeStarkiller]

I currently have a few questions before I start my build. What size screw is recommended for the LED retention (size/length)? Also, how are you guys actually retaining the LED/Heatsink? Is the screw just putting pressure on the side of the heatsink locking it in place, or some other method like actually screwing into the heatsink itself?

Additionally with the B/B/W Tri-Cree, are you guys using both blue LEDs at the same time for the main blade color? I would assume if that were the case, that you would just connect both LEDs to the same main outputs on the Crystal Focus 7.5 board and the white would be connected to the FoC by itself...am i right?

I would really appreciate any advice!