I went from a JP 8'2 x 32 124l Widebody to a 7'8 x 30 115l Starboard Hypernut, and found the stability very similar.
I reckon something like the 8'0 x 31.5 133l Hypernut would be around the right size.
If you think you need to drop 10-15l from a more conventional shape , then you probably need to be looking at dropping twice that if going to a short stubby shape.
Only way to truely know is to demo if you can. These stubby boards all seem to have their own very unique character.
Good luck