150mm....nice size--very big...bigger than my biggest packard shutter!!
you may want to mention that an 8" board will allow a packard shutter that opens to a maximum of 4" diameter and a 10" board will allow a 5" opening packard...so a shutter for something 150mm will almost certainly have to be one of your front mounts to allow full aperature of the lens to be utilized--unless the packard is mounted in the camera to a very large front standard board which the "smaller" 10" and 8" boards attach to.