I sailed the Mono-cat a couple of times back in 1979. I worked for a dealer who let me take his out to play.
As I remember, it was a blast. Tried to make it pitchpole, but couldn't (something that a 19 year old would do
I also remember that there were some severe quality / longevity probelms with the boats and that's why they stopped making them. The hull / deck seams leaked badly and the ABS hull material would delaminate from the styrofoam flotation. There were a couple of "derelict" boats in the back lot of the dealer that were unsalvageable.
Matt M. might have more inside info on that, though.
I'd look very carefully at one of these that was 25+ years old.