Just my opinion and all that I have spoken too that has flown one! Avoid!
The original design is very short coupled with an inadiquit tail plane( too small)
It has been taken over by 3 people each re designing it. I was in contact with the current owner of plans and he redesigned with longer fuse and larger tail plane which apparently made the plane more stable? Mine was original and a hand full on the calmest smoothest days... It was very unstable! A cfi once told me he had to ferry a supercat only 30 nm ,but he ended up turning 180 and landing , stating he'd never fly another supercat .. I named mine happily " supercrap".. IMO. Stay well away and I could also throw in all the fatalities( 1 of which was not structural).. 1 fatality was the 2nd owner of plans and redesigner. The left wing failed ! The only good thing about my experience was "THE EXPERIENCE ". Fly that contraption well, and you'll fly anything well! The nieuport is a puppy in comparison
Here's a vid of the pitch and slip/ skid issues more so on final ,keeping in mind it was a very smooth calm day . Hope this helps and is my opinion only.
I know it's a very late reply!lol. But it may help others thinking along theses lines?