Best way is to terminate the wires at the buttons, leaving ample length at the exit. Once you've decided where those terminate (at the M-Unit or to the frame for a ground) wrap a piece of tape around them and hold them in place. Then rotate the bars lock-to-lock (left and right). This will show you how much extra slack you need for a Lefthand turn, and conversely how much bowing occurs for a Righthand turn.
I use rubber coated P clamps along my backbone to allow the looms to slide through, but sufficient to retain them from being kinked or torn out.