I know thermal pads will make a difference but I mounted mine directly over the original ram heatspreaders without pads and they work just fine.
I had the same problem with mine. I'll take a close up pic on my rampage IV Extreme setup for you.
Close up
My old UD9 setup with 1 plate between each pair. I needed to use a third ramplex to cover the last stick.
Hope this give you some ideas.