What hole for a Betax no 3 shutter?

Hi, I've recently acquired an old Wollensack lens mounted on a Betax no 3 shutter. I need a lensboard for it to use on my Sinar Norma, what hole diameter would I need on a lens board? Most ebay listing seems to have holes for standard Copal shutter sizes, is there any one Copal size which is close enough and might work for a Betax no 3?

many thanks

The Betax is mounted on a flange, which is mounted to the front of the lens board. So the flange lip would have to fit through the hole. As I remember it is slightly more than 52mm. That's not close to Copal sizes (42mm, 65mm).
Jon