Did he shoot a 52? I see a 53 in 2009. That was on an SSA of 67.0. The SSA for McBeth's will probably be right around 67.0 as well. Maybe higher if they combine rounds.
Nate and Avery shot 55 in 2008, on a course that was about an SSA 69.7.
And in 2006, Barry shot 57 on an SSA 71.4. It was only rated a 1076. I think I commented at that time that his round broke the SSA/rating table. Chuck disagreed, of course. (Looking at old results, looks like SSA for that round was maybe closer to 71.2 than 71.4 -- but whatever -- I got the 71.4 from something Chuck published.)
I think McBeth's 52 is better than any of those, although it's obviously impossible to compare just going by scores and SSAs, with all the changing rules and whatnot.