Saucon Valley, while a wonderful institution, could host the open from the outside the ropes perspective, but, for all three courses, from an inside the ropes perspective, all would fail on that grand a scale.
The Old Course, aka the Saucon Course, possesses a fairly strong opening nine holes that could hold up, but the back nine would struggle no matter what length has been added (I would assume it isn't much compared to the front, where there are more possibilities like 2, 3, 5, possibly 6, 7 and
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The Grace Course is stronger than the Old, but couldn't host it from an inside the ropes perspective because there would be no room for spectators on holes 16 through 18, especially 18 unless the playground was eliminated, plus the trees behind the 18th green. Besides, that hole would just be a 3 wood wedge for the top guys today unless they moved the back tee across the Shoudy Barn entrance road, then it would become a driver 7 iron kind of hole.
The Weyhill Course would be better from an outside the ropes standpoint, but it would take millions to get that course ready for an open, plus the original 18th would have to be completely redesigned.
By the way, what holes were lengthened at the Old Course? If someone has the new yardages, please let me know so I can add them to my file and update the My Home Course profile accordingly.