I put 50mm Gravelking SK on Atlas rims on my Sam last week. Tightest spot is the fork crown. If I pump them up past 30ish PSI, they rub. I'd say 50mm is the uncomfortable max tire size; 48 is likely the comfortable limit. I'm fine with the current setup and will keep running the Gravelkings, but anything larger isn't really an option. There's solid clearance all around on the rear, though.
I had Snoqualmie Pass tires on there (Dyad rims) underneath SKS fenders last year. It was very tight, finicky to set up, and there wasn't much clearance for anything but water to splash up in there. I went through some deep mud once and it was a hassle to remove the tires and scrape mud out just to get the bike rolling.
My Sam is a 2012 or 2014, so sidepull, but last year I had canti posts added and run Paul Motolites.
Erik, Philly