Hey Trey-
At the TAB show at the Fillmore, Tim & I split signal from his U89s. I ran it into a V3 with the 100 Hz bass rolloff and was very glad I did. There was still no shortage of bass. I ran the next set without and wish I had kept it on the whole show.
The V3 has a 6dB per octave rolloff, which allows for a lot of verstatility for the amount of bass you want to rolloff. The V3 has rolloff at 50Hz and 100Hz (settings 2 and 1, respectively).
The U89 is also a 6db per octave, but has a different start position at 80Hz and 160Hz.
If the 100Hz setting on the V3 leaves too little bass for you, turn it off and turn on the setting on the u89.
Assuming your V3 HPF filters are in the low filter settings, then you have 3 options to work with!
See you at Red Rocks!
Phil