Which flats with a maple fingerboard?

I like Labella Deep Talkin' Flats personally.
Remember, the fretboard material isn't as big a part of your tone as a lot of people make it out to be...unless of course you are talking about a fretless bass.

On a fretted instrument, take a look, the strings don't touch the board It's just the combination of the wood with the rest of the body that alters the tone.

Now, as for the strings, the labellas are pretty high tension, and wonderfully glass-like smooth.

 

LaBella's or GHS Precision flats will enhance that bass or any Jazz. You'll get that thick, rubber/clack thud.
D'Addario Chromes to me are not old school flats. They are too chimey.