whats the advantage of these besides the extra length?
Im planning on trying to run 5 290's per board and have been reading about problems trying to get windows to see all the cards and people having to short certain pins in the risers to get it to work. Do these take care of all those issues? Do these cables meet the industry standard for load tolerance and insulation etc.. all it takes is one bad cable for the whole operation to go up in smoke?

side question to anyone: could you recommend a 1350w psu gold with 4 pcie 6 pin and 4 pcie 8 pin connectors? ( will a 1350w be enough for 4 R9 290's (non x) Tri X (sapphire) cards (and nothing else)? I was told they take ~275w each- have I enough headroom?