To be honest, nowadays I don't use the Mastering EQ at all (used to pre-OS3) but now all I tend to use is a custom Compressor preset based on the Low-Boost preset, but turned WAY down. Essentially, it doesn't change the EQ much at all, just evens out the low-end response (like a Finalizer) because I think the basses tend to vary quite a lot in the low end.

On the gig, I pretty much always have subs (either one Mackie 15" for small gigs, or two 18" passives for outdoors), so I'm always looking to even out the bass response.

But since OS3, pretty much all of this is better handled by the per-part EQ than global stuff. On your oldies stuff, try rolling that high end off the drums (not just the HH's and cymbals) and it all sounds a lot more authentic!