Just installed some STOLspeed VG's on a Kitfox 4 - 1200 powered by a 912UL and here are some non-scientific numbers that we noted. This is the 4th or 5th set of STOLspeed VG's that we have installed on various aircraft, all with slightly different results, all with mainly positive results. First off, on this one we did the staggered installation which was new to us but since it was tried before we felt lets run with it, especially since it is listed on the STOLspeed webpage under Kitfox. We went as close as possible with the installation instructions as provided on the webpage and here is what changed; All test's flown dual occupancy, app. half fuel at 3000' ASL runway and 4000' ASL circuit elevation, standard day.
Climb increase 200'/min from 500' to 700' Cruise increase 3 to 5 mph approach speed drop (solid feel) by almost 10mph - unable to power off stall the aircraft with stick all the way back from cruise flight configuration, merely nose nodding at below 40mph through a 5mph up and down motion. WOW!!!
...and than we put on the Horizontal Stabilizer VG's at 30mm intervals and taped the hinge.
Lets just say that there was a speed drop in cruise, a heavier feel to the aft stick once flaps are set untrimmed and little to no "positive" change in flare, except maybe a bit of over flare if you were not ever so gentle in your round out and/or deceleration phase. Not sure if I like them or not. Felt good without them and in my opinion taping the hinge, if you really must, probably is all you need. I'd take the faster cruise speed over an over flare on landing, thank you very much, all I am looking for is a nice three point attitude that is holding right until touch down. Maybe a 60mm spacing might be better, in either case more testing is needed. Maybe with a heavier engine up front like a Subie or big Jabi, they may make a bit more difference, but with the 80hp Rotax and the Moment Arm at 12.32 I don't feel they are that much an improvement. Just our experience and two bits.