Now that's interesting. The low B (5-strung) is about 61Hz, so if you rolled it of at 40, you can't be missing much. It's an interesting thought. Does it clean up the sound any?
I play 4 string basses...
Low "E" is 41.204 Hz
Cutting there instead of higher seems to fill out the low end a bit better.
I roll my guitar off @ either 80Hz (usually ) or even 120Hz if it has too much bottom so it doesn't butt heads with the bass.
I also usually filter everything above ~2600Hz or so, sometimes half that on the bass ( higher on guitar ) which seems to sound better to me.
The HPF/LPF settings help a bit with cleaning up the sound as they remove inaudible/unnecessary stuff that adds to the mud factor.
What really helps clean up the signal chain for bass is reducing the distortion levels in both the amp & preamp settings.
That kills the overall gain in the preamp & amp sections a lot, which seems to be more desirable for bass than guitar.
Gain staging is critical if one wishes to dial out the dirt.
Other things I like to do that enhances a "non-bass" sim for bass use is use the "Fat Style" transformer setting and the C414 mic...