Denney Aerocraft Company Model 4 brochure from June of 1992 lists VNE for standard Model 4 at 125 mph, and 145 mph for the Model 4 Speedster.
There is however mention in the brochure about the Speedster having a thicker windshield for the higher airspeeds it flew at (which was advertised with a cruise of 125 and top speed of 135. fwiw, I flew that plane and can verify it actually did those numbers or more, and all on a wood 3 blade GSC prop no less!)
Relative to this discusssion, it is my opinion that maximum structural cruising speed is much more important to the everyday Kitfox pilot than VNE.
The Vno is 98 mph for my Model 4 -1200. When dealing with lots of turbulence I adhere to that number like religion as it is a lot more likely exceeding that airspeed number will potentially cause structural damage to your Kitfoxes airframe
Ironically, my Kitfox is the first plane I have ever owned that I had to pay so much attention to that number, as my other planes aren't fast enough to get close to their Vno number. And even though my Kitfox is a float plane, there are times I have to work to keep it under that number
So many times I read about peoples reported speeds and wonder how it is that we have so many slow Kitfoxes? My long winged 80 hp 912ul Model 4 on amphib floats will top out (in perfect conditions with WOT) at just a tad under 125 mph. I've demonstrated it many times to my float plane buddies.
So when thinking about getting over 130 from a M4 Speedster it really shouldnt be that difficult. (Fwiw there were many aviation articles that confirmed those speeds). Besides having a shorter, less draggy wing, the factory Speedster was well built and pretty slick aerodynamically with a radiator fairing, well fitting wheel pants, and all streamlined struts (wing, jury, tail, etc). Overall it is just a good example of how to make a Kitfox faster IMHO.
I heard the first 914 powered Model 4 even with the long wing could hit VNE straight and level, and at altitude was 150+ mph. Later the Model 6 proved those speeds again on a long cross country from Idaho to SunNFun, but at altitude. (As I recall 185 mph on one stretch at 21,000 ft).
Our Kitfoxes are more capable speed-wise than most know...