The first one, replacing the pot meter with resistors did work for some time on a first servo. You have remove the nob of the gears that prevent it from turning around and force the pot meter to turn over all the way. Then disconnect the wires from the pot meter and put some resistors in between that match the pot meter's value. But my soldering skills aren't that great so it came lose very quickly and I burned the second one I wanted to modify. You have to get these soldering and new resistors into the very limited space of these micro servo's.
Since the internals are so limited I looked for another way to get this done. I found on the web you can in fact glue the pot meter in the center (has to be in te center!! power on servo to center) and then you only need to drill out the hole on the gear for the shaft of the pot meter so that it can turn freely. Removing the nob on the gears for free rotation is still needed. But this way you don't need to soldering anything. The pot meter is than functioning as a simple resistor since it's never moving anymore. It's always indicating it's in the center position, like you simulated with the resistors in the previous method.
The last option is to buy them modified :).