....I'm not familiar with a programmable (for end points) retract servo. If the servo can be adjusted/programmed for the end point, does it draw current at each end? I've always set retracts up using one servo and it's worked.
Just like any other servo, it will draw current if it is loaded. If the end of travel, the servo is not loaded, it will draw the minimum current the servo is rated for. If it is loaded..........
Now, since you seem to be a little old school (take it as a good thing, LOL) you are most likely going to set up the retracts where the servo is not loaded when retracted (arms 180 degrees apart, links pulling against each other) and lightly loaded when extended, using the gear design to take the load. Then almost any servo with "extended" end points should work. I have used the end point programming on my radio to arrive at the same configuration using a normal servo in the retract job.
Rafael