Phil,
Thanks for weighing in. As we were discussing yesterday, the writing style sure seems to bear Tilly's imprint, and there were very few men who had the breadth of knowledge of Philadelphia golf, the clubs, and the people, who might have written that, with Tilly being primary among them.
From my perspective, if Tillinghast said that Wilson, Crump, and Smith laid out Cobb's Creek, and having the personal relationship(s) with each of those men that he had, that's about as good a proof as one could ever have of the verity of the design attribution.
We still intend to continue our research, and plan to visit the city and park archives this month, seeking a Holy Grail that would be in the form of a hand-drawn blueprint, and or other contemporaneous written accounts in the official city records.