Where did you see a bad review? One thing to consider is that Jack built virtually all of his basses to order and he was not reluctant to build some pretty unique fetures into them. A bad review might be someone's "neat idea" that Jack built and the owner thought better of later, or the next owner found it annoying.
I have played a lot of Jack's instruments and own a Read Model J, and IMO it is a top-shelf bass. The fit. finish, neck profile, balance, tone... all excellent. One thing to consider is having the bass shipped to Jack's shop, and then on to you. That is what I did with mine and Jack was able to not only tell me a lot about what had been done since it left his shop, but put it all back to "zero" for me. A little extra shipping cost but well worth it.
Feel free to run some info on the trade-bass by me (PM, email). There is a fair chance that I have seen or played it. Definitely send an email to Jack and ask him what he knows about the bass in question. He has been a bit out of the loop due to family and business commitments, but he is still supporting his products.