another dang spooling question

Have an old garcia 6500 that I was considering sandwiching some braid between mono base and mono topshot... main idea is to add extra yardage in case a jack or something big runs out my line.. Definitely dont want to deal with a braided backlash, thats why i rather have the topshot mono.



Is that an advantageous thing to do or will it be pointless or even a disadvantage?



Would that set up negate the casting advantages of braid?



Guesstimates on lengths for each section?