Good info here! Here’s a trick I was taught that made me go WOW that’s the easiest way to do that. When you want to find center of rails to do fronts off temp skip. Get a stick of 3/4 conduit notch about 1/2 inch off one end 1/2 way thru. This end goes on rail and out the opening. Put a pencil on the end and draw an arc on the floor. Now do the same on the other rail. The two arcs will cross each other in 2 places. Draw a straight line thru the 2 Xs back to edge of hoistway. This will be dead center of your rails every time. Length of conduit will depend on how far back your rails are but you’ll see real quick how long you need.