Best stereo effect is to run neck PUP to your low frequency rig with either 12's or 15's and bridge PUP to a higher frequency and/or overdriven amp setup run through 10's. Ends up sounding like 2 bass players playing in unison.
For the huge stages that he would work on wireless is the only way to go. I made my stereo patch lead from a 25' stereo mike lead with a female mic canon connector attached via a male canon connector with 2 mono tails 10' long each. All up it was 35' long which is around 11m in metric fed into 2 Boss DI units then into separate channels on my 100w Marshall Super Bass Amp Head and finally blasting out through a 4 x 12" 25w greenback celestion slant front quad box. The 4 x 10's setup most use today had only just started to become popular as I got married and stopped gigging in mid 80's. These days I am happy to use just a 10" or 12" combo for either guitar or bass as they have come a long way in the past 30 odd years since I last was gigging.