Skot- I couldn't remember if your Vixen's gear had that fairing mod or not but sure sounds like it has.
Paul- I've had my model 4 with a 912uls to 132 mph wide open throttle many times. Usually at 3,500 feet or so altitude with the Ivo Lite prop. with rpms
in the 5,600 to 5,700 range for just a minute, two at the most. I have no wheel pants, spinner, jury strut fairings or horizontal stabilizer fairings. I do have gas cap fairings and strut fairings and the wide body modification along with the razorback mod. Empty weight 659 lbs.
My airspeed indicator and gps are within 1 mph on a zero wind day. We actually have quite a few zero wind days here in Phoenix.
Some years back Michael Gibbs had the exact same model 4 Kitfox with the same engine but with wheel pants, large spinner and streamlined jury struts and an Ivo Medium prop and he could hit VNE (140 mph) in level flight under the same conditions. I can't recall what his empty weight was but I think slightly heavier than mine. He also climbed that Kitfox up to 17,999 feet in altitude and still had a little more ceiling left.