When I mentioned the ballscrew lengths, this is what I was talking about.
Perhaps this becomes more obvious when I get the machine in front of me and I remove the ACME threads.
edit: perhaps the machined length of the ballscrew at the motor connection is 10mm. This will match the ID of the Bearing I listed. BUT....
But what about the coupler? I'm still confused as to what coupler size I should use. Its probably best to use the largest diameter machined down from the ballscrew I imagine.