LEDgardener

I'm building these from a kit and they give you exactly the number you need which of course i screwed a couple up and ordered more but they're thicker than the ones that came with the kit. Does it matter?

With thermal pad do you mean the sticker to attach the heatsink?

Check the thermal conductivity of the pads if you can. Should be in watts per meter-kelvin.

Usually you would want to tighten down onto the pads well in either case to create a bit of pressure on the pads.