Ben,
This is really excellent work--the artwork, of course, but the routing is, too.
I really like your solution for getting to the 3rd tee by rotating the second hole, and like your tenth a lot, too. If you weren't trying to build 18 holes on the property, but just 16 or 17 (following Sean's suggestion), you could preserve most of the rest of the existing St. Olaf course. 17 holes might be perfect, thanks to Frank's par 3 on the big course.
I'll now comment on your proposal and others for the holes in the dunes along the coast. Regrettably, I had to scrap plans to play the St. Olaf this year, so I can't say which holes from it should stay or go.
Ben's 3rd hole is a popular choice through a valley in the dunes (my 11th, Michael's 10th, Thomas' 4th).
Ben recognized a great tee location for his 4th hole: perched on the ocean's edge, it allows the player to avoid climbing a serious hill with the 4th tee shot that would be necessary if the tee was just a bit inland (see Thomas' 5th tee as drawn).
The holes on the ridge along the ocean are obviously all thrilling, but I wonder if the fairway for Ben's 5th/Thomas' 7th is just too narrow, with steep drops on both sides.
Ben's 6th would be even better IMO if the fairway were widened a little and perhaps the tee pushed back so that the large hill between the LZ and the 7th green came into play strategically--so that players were forced to choose between an aggressive line along the ocean and a blind second. (My 8th has the same strategic feature, playing the opposite direction.) I think Frank recognized this the way he drew Thomas' 8th.
On Ben's 9th and Frank's 8th, I'm not sold on the idea of putting the green behind the ridge, blind, with all the other trouble lurking unseen in the form of the blowout and the burn.
Ben, perhaps you could squeeze in another par-3 across the burn, after your 4th or 9th hole, similar to Thomas' 6th, in order to help reach a target number of holes without replacing the whole existing course. Playing the 10th toward the existing 2nd green would help, too.
My one other comment on the inland holes: I really like the green site for Frank's/Thomas' 15th.
Great contributions from all and thanks again to Frank for sharing.
Best,
JB