nice comparison Matt - it would be really great to get you onto the 877 or 1107 for comparison also as they were designed for similar usage, namely to pump, glide and turn well, without sacrificing too much top end, so on paper should be right between the Spitfires and Progressions.
They have custom sections optimised for high lift without stalling but also with a low drag through most of the range. Top end is similar to ART but much better low end and pumping. It would be possible to gain even more low speed lift but you start to pay fairly heavily in drag at normal foiling speeds…
Planform is reasonably high aspect ratio for the glide, but not extreme for the turns, and tips are designed to breach easily without venting.