This design (V-stub) is my thought. It may have existed, but I have never seen it anywhere.
Simply because when the wire is cut and bend, it is the measurement from the threaded screw which is required & used.
If someone wants to simulate the design, then he has to add to 58mm, the length from screw to the point of separation of coax. This lenght is inside base and is about 15~20 mm depending on individual make of the mag mount whip.