Re: Ideas on securing wires inside mast?
"One thing I question is how do you satisfy the AYBC requirement of supporting the wire every 18 inches "
I suppose that means doing what the utility companies do on powerlines. Run a separate steel cable, secure the other wires to it every 18". Oh did I forget? To mention do that while the mast is down, now insert the whole bundle in your conduit and secure it from the top, let the steel cable take all the weight.
Sometimes there's no easy or practical way to retrofit.