Modifying a case length gage at home

[Ohio3Wheels]

I shoot a goodly number of straight walls these day and while they seldom need trimming they now and then need the mouth cleaned up. In the case of the 45-70 enter the Lee case length gauge and holder. Quick easy and saves wear and tear on the wrist from either the Forester or the Hornady/Pacific. Problem comes with the 40-65 cases, Lee doesn't make one and yes I know they'll do a custom one but I'm frugal and I have a Sherline lathe. My thought is to get another 45-70 (both are 2.1 length) and reduce it so it will fit the 40-65 case. Has any body here tried that?

Make smoke,