I'm making a neoprene tuiliq using the qajaqusa pattern; I wil sew the 3" 1-side neoprene along the hem. I'm unsure how to size the bottom (hem) of the tuiliq. I've seen several instructions relating tuiliq size to kayak coaming size (Chris Cunningham, Duane Strosaker and others), but they don't specify how they measure the coaming: is it the outside (largest), or the inside where the tuiliq bungie will rest, or the size of the actual hole where I fit (smallest)? I tried the qajaq usa forum, unfortunately no answer there.
My kayak is a Yost Sea Rider, the inside cockpit (hole) is 16" x 22", the part where the bungie will rest is 3/4" larger than the hole (66" circumference), and the outside of the coaming is 1.5" larger than the hole (71" circumference).

Thanks for any advice you can provide.