Holy thread drift Batman!
The Sumacs we're interested in are the Buckhorn, Smooth & Fragrant Sumacs all of which produce seed heads of red, fuzzy berries that can be brewed into a tea & chilled to make a very pleasant pink lemonade facsimile.
Poison Sumac is more shrub-like and produces white berries. They're very easy to tell apart once you know what you're looking at. Incidentally, I know a local Forester who has a variety of woods including a sample of Poison Ivy. (I'm not nearly crazy enough to attempt a boat from that)
A "massive Sumac" is almost certainly Tree of Heaven, aka Chinese Sumac. They're very invasive and not particularly interesting as wood but I may use one to build a canoe someday just to rid the world of one and see if I can render it's existence worthwhile.
Anyway... I have a Goldenglass Sawyer Summersong, a Bear Mountain Freedom Solo stripper (16' 3" version) built from Aspen & Cherry, A John Winters designed Raven stripper in Eastern Larch (aka Tamarac) & Sassafras and a Northwest Canoe Merlin stripper in White Pine & Cherry that I'm hoping to actually finish before the snow flies.
I was waiting to post in this thread until I'd paddled each enough to relate my impressions of them but I screwed up and derailed the whole stinkin' thread a bit (oops... As you were...)