Ok, on GPURISERS.COM I found this in the FAQ…
How do you properly power a GPU Riser?
Our risers feature two 6-Pin connectors and one Molex connection. Only one of these connections is required to fully power the GPU Riser safely.
How many watts does a GPU Riser consume?
Our GPURisers.com branded risers consume 4~5 watts when GPUs are properly powered.
When is a GPU properly powered?
A GPU is properly powered when the usage in watts is less than the power being delivered to the card via onboard 6-pin and 8-pin connections.
What are the power ratings for 6-pin and 8-pin connections?
6-pin connections are rated for 75 watts, and 8-pin connections are rated for 150 watts
This tells me that as long as I am using both connectors on the card then I should be safe powering the riser with the molex…
They also warn about the SATA adapters