Tom,
As I mentioned earlier, I think it is now clear that the Francis Land Swap happened in 1911, and not in 1910. Combine that with the Macdonald letter from July 1910 and we can safely say that Merion bought land, and then designed the course, and not the other way around.
I believe we can also now safely say that no routing was produced for Merion East prior to the appointment of Hugh Wilson's "Construction Committee" in early 1911.
We also know that work to determine a routing began quickly, much like it did at Cobb's Creek, and was determined and finalized within about three months, done with topographical maps, surveying, and such, and that it was finalized in time for the land swap sometime before the end of April 1911.
I think that's a reasonably conservative synopsis of what we know based on the evidence that's been produced to date, and not counting anything yet you mentioned earlier alluding to 5 different "plans" etc., that have recently been found in the MCC minutes. I'm reluctant to bring them into the discussion only because they haven't been publicly disseminated yet.
What seems still in question to me most fundamentally is;
How much did Macdonald/Whigham help with the routing, beyond helping them pick the final one of the five in April of that year that you mentioned the other day? (based on the new MCC minutes evidence). Certainly, it seems that their window for having done so is rapidly shrinking.
If they contributed anything more, it appears they would have had to have done it during the two days at NGLA in January, but there is really no mention of that happening in Wilson's account, or anyone else's. Wilson specifically stated that "our (referring to the committee) problem was to layout" and credited M&W with giving them a "good start" in understandng the "principles" of great holes...nothing about providing Merion with any hole designs, much less a full fledged routing.
Moreover, whatever might have come from those meetings at NGLA, we also now know it certainly wasn't any finalized routing plan, because we now know those plans were being worked on and finalized for the next 3 or so months.
In any case, I would have loved to have been a fly on the wall for those meetings!
I'm wondering how much time they spent on the course, and whether they played. I can't imagine being out there and not playing, but we don't know for certain. After all, it was a brutal winter, at least in Philly, but Southampton doesn't get much snow, so who knows?
Also, I am still perplexed about the source(s) of the 6/7 month Hugh Wilson overseas voyage. For some odd reason I still think it had to happen in 1910, and we know that in American Golfer that year AW Tillinghast mentions that Hugh Wilson has not been around for some time for tournament play, but also talks about Crump coming back from Europe, so it's not a clear reference.
In Jim Finegan's GAP Centennial book, he mentions;
"Hugh Wilson spent some seven months abroad. For the most part it was the shrines of Scotland and England he was playing and studying, though on occasion
he visited some less known courses, such as Stoke Poges and Swinley Forest. After all, the new Merion course he was charged with laying out would hardly be seaside."
I find it odd that Finegan mentions specific courses...I don't recall anyone else doing this and I'm wondering his source(s).
One possible avenue of further exploration is to see what type of archival visitor logs those two clubs might have.
In any case, I believe more of the picture is coming into much sharper focus.
I think the key piece of the puzzle is your finding that the triangle shaped piece just didn't fit, and ironically, it's exactly what Richard Francis and the Merion Construction Committee discovered as well.