I fit 29 x 2.2 continental race king mounted to cliffhangers, I think actual was 54mm. It was so tight that the rear tired rubbed the paint of the chainstays. I would recommend keeping it at 50mm or below, especially on modern rims.
I know the old catalogues said 700x52 nanoraptors fit, but a tire that actually measures 52mm is going to be a tight squeeze.
Ben