RE: retracts or fixed?
Have you seen the advertisement for down and locked? It's an electrical retract system that looks real good to me...uses an electric motor to turn a jackscrew. From what they say it uses very little power from the battery and has all kinds of fail safes....
You send them a mechanical or pnumatic retract and they fix it up and send it back to you.
If I have any trouble from my current system I'm gonna give them a try