Has anyone tried a dual water pump setup?

Just wondering if anyone has tried to use two inline pumps in their water cooling rig to keep the flow rate up?

I tried it for a week.
I did get better flow rate, as tested filling 5 gallon buckets vs. time, but I didn't get any better temps. My waterblock is the low-flow Gemini, and didn't seem to benefit from the higher flow rate.
Someone else's block may though.