Done plenty of tv wall mounts for myself, but never come accross this prob.
I'm going to wall mount on top of the mantle piece, and bring cables down to the right hand side of mantle piece, in behind the plasterboard, to meet with cabinet on the floor. How do I get passed the joists? Since it's not a vertical cable drop, which is basic, how do you overcome this obstacle of attempting to pass cables through joists. Surely, there is an answer, without bursting open the plasterboard.