I'm considering adding a second banjo, and am looking at the Oneway.
But Oneway tells me that I'll need to tell them the dimension of the gap between the ways, and that any deviation from 1 3/4" will require special machining.
I measure the gap on mine at 1/64" over Oneway's dim. (1 49/64").
I don't see that as an issue - I'd be much more concerned if your gap was smaller rather than larger. If you consider the clamping plate on the underside, if equally spaced in the gap it would amount to an extra 1/128" on either side in the gap.