The only problem with the ball end wrenches is that unless you get one with a ball on the short end, if the rod is tight, you can't get enough leverage to turn it.
+1
A deeper channel could be a solution for better access but maybe it could damage the headstock solidity so...anyway, finding a solution is not my problem.
My problem is that i have recently purchased a new Mj4 and i can't adjust truss rod because:
1- bad access for wrench key
2- bad edges in the nut ( seller has checked truss rod before sending me bass, that's probably the reason )
Result is that key don't grip.
Topic has been created on bassesbyleo forum (see link in the previous page )
G&l asked my serial numbers. Hope they could fix the problem by asking me to return them the neck and sending me back an operational new one.
( i thought to ship neck to luthier to dig channel and replace nut but nut is welded

)
Otherwise, i would be forced to return bass to seller and would loose money i gave for duty ( i live in France )
I'm waiting for news..
Except this matter, it's a great sounding bass with a convincing pbass sound once molded with preamp. Both pickups together sounds great too, solid and sweet with a compression in slap on D and G strings. Due to the lack of tone control, difficult to reproduce Jaco's tone but bridge pickup sounds well too.