Andy McCluskey from Orchestral Manoeuvres In The Dark also stribgs his bass "upside down".
I've got a guitarist / bassist friend of mine - Marcello Marinelli - who is a leftie. He learned to play using his older brother's right handed guitars - simply turned round to the left hand position, with the low E closest to the floor.
It was funny at the Wembley Guitar Show years ago when he asked to try out a Gibson Les Paul, and then flip it over to play . The rep said " wow, I've never seen that before".
Chello's older brother Rico was also there, and he lost his right hand aged 16 in a horrific accident. He too asked to try out a guitar. The rep said, "are you going to play this one upside down too"? The look on his face was even better this time around as Rico answered "no, I play right handed", then proceeded to take off his right hand and replace it with a new one specially made to hold a plectrum! The poor rep must have thought he was being filmed for a hidden camera tv show! Hahaha