Believe it or not, truss rods are optional on those things.
The one I played did not have one . Some people describe a really big neck as being like a baseball bat ... this was bigger .
Trust me , it did not need a truss rod .
And it truly possessed a terrible beauty .
There used to be a clip of Wishnevsky jamming with some guys on YouTube , his approach playing was as odd as his design sense . Kind of random glissando but without a tonal reference . Very strange .