RE: power expander pin connectors
I would not worry about the PowerExpander side. The pins on the PowerExpander will not wear out or loosen. The sockets in the male connector that plugs into the PowerExpander will wear out first. No matter how you look at it, the male coming from the servo side will wear out first. Even if you use a small extension, the pins will be on the PowerExpander side and the sockets on the servo extension. I would just monitor the situation and if the connector starts to seem loose replace the extension. You want to minimize the number of connectors between the servo and the PowerExpander, they cause more voltage drop than a lot of 22ga wire.