Looks promising - when I did something similar (Knog to Pletscher rack on a Raleigh Twenty) it needed several changes to the design before I was happy - let me know if you need the kind of modifications that can't be done with a file...
Fits great! Could maybe be a few mm wider or larger in diameter but not really a big deal. Also might be worth having the bolt be on top of the rail not underneath for more clearance but this certainly works
32mm wide, 30mm diameter, bolt on top.
Putting the bolt on top requires quite an increase in diameter (from 25 to 30mm) to avoid very thin sections, which in turn means a significant increase in print time - probably worth mentioning if it's being done as a favour...
Looks promising - when I did something similar (Knog to Pletscher rack on a Raleigh Twenty) it needed several changes to the design before I was happy - let me know if you need the kind of modifications that can't be done with a file...