Well it also had a comp tip and that was a problem for performance oriented sailors.
Of the Foxes I had sailed none had a Comp Tip. I think that the Comp tip was eliminated shortly after the boats introduction.
I agree with both John (on the rig) & Wouter (on the smaller sail area). PS the sail area thing was in toatl deference of the formula 20 rules as originally written in EU
But let me throw this in. By the time the Fox was introduced in North America the I20 was already established as the pre-dominant (only) spin cat class in the US. We did not need another big spin boat.
Eyes then turned on the Formula 18 and we all know how that is going