power pro will not eat your guides on your avid. they are Fuji Concept or Fuji Alconite. they will not be phased by braid. the only guides braid eats into are cheap ones that are just stainless steel (ugly stik, lightning rod, etc). 50lb power pro has not harmed my avid but it has dug grooves in my ugly stik and lightning rod.
how far can you cast? however far that it, double it. put that much braid on it. fill the rest with mono. in other words, if you can cast 100 feet, then fill up the spool with mono, and then tie on your braid and spool on 200 feet of braid. this will conserve your braid since it isnt cheap. and it doesnt get "old" either so if you want to you could take all of the braid off your spool and just flip it around...tie the end your lures used to be on to the mono backing, and it will be like fresh again.