Speaking as a bassist who has never had the opportunity to play GJ baass, but who plays a lot of 4 to the bar swing basson early swing tunes, many of which are played by GJ bands also, I thought the threads that were going on were really interesting - shame it petered out so soon. BTW, I recommend pizzicato strings for GJ, as they are somewhat percussive and short on the sustain side IMHO. For uprigtht bass use the amp that colours your signal the least. ie use settings that do not sustain the notes artificially, and at the same time does not emphasize any mid range nasally thump on the attack of the note - the ever evasive sonic clarity! Best I have heard (and seen) is that Rosenberg Trio Samois video with Berelli and Christian Escoude sitting in.