I've been trying to get this right for a few years now, with varying degrees of success.
I used to use a splitter box into a VTbass and send that to FOH, worked well but it did effect the low end in a way that I couldn't fix (kind of fairly wide cut around the 500Hz region).
At the moment I prefer to use the VLE vintage loudspeaker emulator filter on the Markbass LMiii. I use this with the VPF scoop control and works really well, many engineers have complimented the sound. This technique suffers at the hands of the cabinet though, the more full range the cab the better this technique works.
I am still searching for the tidiest way to do it, as I personally prefer bass cabinets with no tweeters at all.
I am curious to try out the Two-notes audio and AMT electronics impulse response loaders, load in a nice 8x10 and you're rocking...