At the performance of FIDDLER that I attended on Monday night, it was announced that the entire rest of the run at the current venue in the Museum of Jewish Heritage is sold out. That didn't sound like a lie.
Also, from what I can tell from Googling, the theater at the museum has a seating capacity of 375 -- but I think it's a bit more for this show, because they added a row of seats at the back of the orchestra, so I'm guessing closer to 395. As I think we all know, the capacity of Stage 42, the theater to which FIDDLER is moving, is 499. And as far as the stages at both venues, it seems to me they're roughly comparable in terms of size. Stage 42 has had flop after flop not because the theater is too large, but for other reasons.