I had a first year JP90 a while back as well, bought it off ebay. Loved the weight and the skinny little neck with the somewhat abbreviated headstock shape. Unfortunately, mine had a maxed out truss rod and I couldn't get it quite playable enough. Sounded great with both pickups on full. In fact that was the only tone out of it I truly liked, but it was a great tone. I thought about replacing the neck, but I didn't want to put a standard Jazz neck on it and didn't want to devote the time and energy to acquire another JP90 neck as they're not too common. So I sold it, at a meagre profit no less. Maybe someday I'll go back down this JP90 road or maybe a P Bass Lyte (quite similar)