Air retracts are no more problematical than mechanical.

A couple of points to watch for.

1. the gear may slam up and down very vast, so you might want to restrict the airflow if this is not done by your valve (although I think Robarts are adjustable).

2. If the movement is too slow this may also cause problems, I have one model where a gear door does not fit flush and if the leg moves too slow the drag from the door will stop the leg from going fully up and locking.

Simon.