I tried out the RS-232 9 pin connector. It is leaky as hell. Try this (at home). Take a 9 pin connector and suck at it. If you can feel the air? rush into your mouth, you know it leaky. Get to work with hotglue gun. That's what I am doing now. But we can't use the connector across the pressurised barrier. It might be easier to just stuff the four wires through a small hole and hot glue the hole.