Hi, I'm new to the forums and crypto mining in general. But I thought I'd share the performance results of some riser testing I did.

Specs:
EVGA GTX 750Ti FTW (has 6 pin power connector)
Intel G3220 on ASRock Fatil1ty Z87 Killer

Conservative overclock: +50 GPU, +500 Memory

And the results (scrypt):
Baseline (plugged straight into x16 slot): 290-299 kh/s

Non-powered x1-x16 in x1 slot: 270-280 kh/s
Powered x1-x16 in x1 slot: 272-282 kh/s
USB powered x1-x16 in x1 slot: 270-277 kh/s
USB powered x1-x16 in x16 slot (gen 1): 266-269 kh/s
USB powered x1-x16 in x16 slot (gen 2): 288-295 kh/s
USB powered x1-x16 in x16 slot (gen 3): 288-297 kh/s
Non-powered x16-x16 riser: 292-297 kh/s

As you can see, there's not much penalty for the riser as long as you're able to plug into a gen2+ x16 slot. If you're plugging into an x1 or gen1 x16 slot, there's a 10-15% performance penalty.

I hope this information proves useful.

Edit: Command line was: cudaminer.exe -H 2 -i 0 -m 1 -l T5x24 --benchmark