One thing I always do for my mandolins is dampen the strings behind the bridge before the tailpiece. I do this with a short piece of leather string, like those used for hiking boots. This will eliminate the natural ringing or resonance of these short sections of strings and give a cleaner chop. This doesn't increase/decrease the bass, but the cleaner chop may get you closer to the sound you are looking for.

One last comment on the Wegens: I use them for mandolin and guitar and like them. A complaint I've often heard is that the Wegens are too thick and heavy. Well, they now have a 1.10 version of their picks and they may suit those who prefer a thinner plectrum.