Hey there! Yes, it’s a wonderful instrument that really shines as a solo “voice” if you spend some time with it. I had a tech guy put the Yamaha preamp back in, as I preferred its sound to that of the Aguilar.
Regarding the trim pot in the TRB6P, I went and opened her up earlier today and turned the knob back and forth while a note rang out. Interestingly enough, it affected the gain of the regular pickups, not the piezos. Makes sense because there’s a blend knob on the bass that allows you to blend in how much of the piezo you want in the mix (or not at all). In any event, I set it at just past halfway guessing that it would give the overall preamp signal a little boost without making it too hot for whatever amp or board it’s going into.
Here’s a brief clip of me hanging on for dear life on an impossibly fast Got A Match? with the JP2: