I've read a few interviews with Jaco that describe him as constantly tweaking the setup of whatever bass he was playing at the time (including loaner basses!).
I wonder if removing the pickguard had anything to do with the possibility that it may have been partially blocking access to the truss rod, which he would have adjusted from the bridge end of neck?
You have to completely remove the pickguard from my 1965 Jazz Bass to get to the truss rod with a screwdriver long enough to easily turn it. While the "Bass of Doom" is a few years older than mine, I think it has the same truss rod system.
I wonder if removing the pickguard had anything to do with the possibility that it may have been partially blocking access to the truss rod, which he would have adjusted from the bridge end of neck?
You have to completely remove the pickguard from my 1965 Jazz Bass to get to the truss rod with a screwdriver long enough to easily turn it. While the "Bass of Doom" is a few years older than mine, I think it has the same truss rod system.