Most Morse cables
have a 3" travel, and my Hurth
(HBW 360A) needs about 1-3/8" travel each way, leaving only about 1/8" room each way for adjustment. There are two holes on the lever, the outer hole leaves no room for adjustment at all as it needs 5mm of more travel according to the manual.
The lever on the top of my transmission is not keyed to the shaft. I found I got much finer adjustment by adjusting it rather than trying to move the cable mount. A few iterations of making sure the trans shift fork was in the middle of its "slop" between hitting forward and reverse, at the same time the shifter was in neutral, and it works much better now.