I agree with your coax choice and have already purchased the coax. It is expensive, but very low signal loss.
Great idea about the vertical wire support! Expanding that idea, I could use a length of braded dacron line instead of wire supported from the masthead. That would allow me to insert the plastic tie straps through the braded line and around the coax and 5 conductor cable and it won't slip down. Also probably less weight than wire and no corroding or rusting. It would also allow me to extract the wires out of the jacket as you recommended and still have the support needed. Thanks for the great idea!
I'll need to remove the masthead and base aluminum castings from the mast to do this. Looks like stainless steel pop rivits used for fastening. Having not done this before, I assume I drill out the SS pope rivets and replace with new SS pop rivets when I'm done? Or is there a better way?