I do exactly what Paul described - I set my master volume at around 80% so there is some headroom "for dramatic volume swells" or in case I need to step out for a solo passage or something. I also have a mark about 10db lower in case I'm in a studio where my output is too hot for the board's input. I used to have these two spots on the master volume control marked with tape but when I had the bass refinished many years ago I took the opportunity to have them inlayed.
I also think Jazzyvee is right in that power amps or "master" volume controls on an amp head want to be run at, or close to, wide open. I think that's the way to get the fullest tone from that last section of the chain. Unless you're in a situation where the idle hiss is too loud and then you need to trim it a bit. Otherwise the preamp gain would be my choice to control the overall volume. Again, we're talking about going for a clean sound - if you purposely want to overdrive the poweramp input you can trim down the output and crank the preamp gain... Etc...
As we've been saying, one of the amazing features of Alembic Series instruments is that the output level does not effect the overall tone like it does on a passive bass. The producer asking you to turn the bass all the way up was assuming that would give them the widest sound. And if it was a Fender P he'd be right. But he didn't know our little magic trick.
Jimmy J