Interesting write-up on modifying a servo. Sort of a mechanical jury-rig to override the pot's signal.
Another way, is to remove the pot entirely, and replace it with a pair of identical resistors, wired in similar fashion as a pot. It might be a little more complicated the first time, but it accomplishes the same task and might be necessary if your servo is a different design (either way works with the Futaba S3004 shown in your write-up). I'm not sure I'd trust some Krazy Glue on the pot shaft.