I don't have a UBass any more, but I've played this exact rig using a custom 5-string Howlett uke-bass and also using a DB. It works really well, but in a rather different style than, say, a Barefaced OneTen.
My old OneTen was very much a Barefaced. It was ridiculously light, and far louder than you'd expect, the sound projected a long way into the venue, and it worked really well IMHO for rock and similar.
My Crazy 8 is a very different beast. The sound is somewhat mellower, but what I really notice is that the sound is far more 'localised' ... it doesn't project so much.
This is NOT a criticism. What it means is that, with the cab close to the bass, it just sounds as if the bass is considerably louder. From a DB point of view, especially at smaller venues, that is exactly what I want. It is actually very easy to forget that the DB is being amplified.
I bought my Crazy 8 pre-loved, and it turned out to have a 'top hat' fitting. That has proved to be very useful indeed. I can put the cab on a spare PA pole and either use it as the main amplification for a DB gig, or as on-stage monitoring for a rock gig where I'm going through FoH.
In this video, that's my Crazy 8 directly behind the guitarist's shoulder:
I was sufficiently impressed with the Crazy 8 that I commissioned Guy to build me a Crazy 88, and that very neatly fills any gap between the Crazy 8 and the Markbass 210.