I got in touch with the VX owner on ebay that had purchased the FFD twin fan set-up and was so pleased with it. He's somewhere in TX and has had overheating for a while, with A/C on, in stop/go traffic, on high air temp days. He installed the twin fan set-up but it didn't help problem. When he contacted the company, they realized he should have been sent the "extreme" package, which is a SINGLE 17" FAN, and that solved his problem. This is consistent with what "Bill" told me.....a single larger fan can move more air than the smaller electronic fans.