I would love to make a trip out to the Island with you, but it may be a while. I don't expect to be back in CNY until early March or so. I was home for Christmas and asked my brother if he'd been over there during hunting season (he had), and he said the Savannah entrance was flooded up to his waist. I've been on the lookout for the kentucky coffeetrees as well as a supposed state champion chinkapin oak in the hickory hill area, but haven't located them yet. My suspicion is that the chinkapin oak is really one of the two large white oaks on the east end of the drumlin.
The ecological history of the Island really interests me, especially the types of trees that might have grown there before it was settled. I have the same feeling as you about the absence of hemlock, even though many areas on the Island would seem to support the species. Same thing for northern white and red cedar, white pine, and tamarack, but non-planted individuals are nowhere to be found.
This Freeman maple thing has me re-evaluating what I thought were simply tall, straight silver maples. I'll have to go out and give them a second look. The leaf pictures you posted look to me like silver maple, but I've been fooled before.
BTW, the hickory hill area seems to be the most diverse on the Island, even though it's obviously been cut over several times. The swamp area at the base of the hill supports tuliptree, black gum, beech, hickory, red maple, and sassafras, and the uplands are where I measured some of the tallest sugar maples, white ashes, red oaks, american elms, and sycamores.
"There is nothing in the world to equal the forest as nature made it. The finest formal forest, the most magnificent artificially grown woods, cannot compare with the grandeur of primeval woodland." Bob Marshall, Recreational Limitations to Silviculture in the Adirondacks