I own the previous BTB 7 string, the one from the Bass Workshop series, the BTB7-NTF. It's a solid instrument and good sounding. Kinda heavy at 5.99 kg but I've tamed it a little bit by swapping the tuners with Gotoh Res-O-Lite GB350 to 5.85 kg. It may seem only a small amount, and this bass never had neck dive issue with the strap on to begin with, but with GB350s, it becomes more balanced between the neck and body when playing it while sitting even without putting the strap on.
My only complaint is that it doesn't really have forearm contour. It's more a beveled body than forearm contour which felt kinda sharp edges when crossing forearm there, especially when playing it while sitting. The newer BTB747 seems to have a larger bevel at the edges where the forearm would cross. I haven't tried it my self but it looks like that it's more forearm friendly.