I head of people saying they hooked up with a monster shark that striped all the line on the reel and durring the fight they attach another line? How is this done and how does this work? Has any one tried this before?
a good number of members have did this. you tie loops in the bottom of your spool so you can have another rod rigged with a snap swivel so you can have a team member grab the line when the loop comes out and clip the next rod to it and cut your line. another way is have a good team and some one that can tie knots quick have a member or 2 wearing gloves grab and hold the line and have another member tie a uni to uni or what ever line to line you can tie fast and trust. both ways will take practice and should be practiced until every member can do each part.
What kind of loop would u tie at the bottom and how do you reel in the line from the other spool onto a full second spool? Would u suggest to always have a back up reel for this or is it rare to hook up with such a monster.
tie what ever loop knot you have confidence in. by time you have to reel the first line up the shark should be tired enough to tie back to the first reel.
Would the dropper loop knot be good?
http://www.animatedknots.com/dropperloop/index.php
Being An Older South Beacher And Fishing With Rene di Dios For So Many Years, I Got To Practace This Quite Often. The Best Way I Know Is Mono To Mono With A Uni. Like monoxide Wrote Find A Knot You Know And Are Comfrontable With, One You Can Basically Tie With Your Eyes Close. But I Do WARN YOU...You Have To Do It Safely And Swift. One: Know Your Line, You Dont Want It To Catch Anywhere In Your Guides. Two: Dont Ever Try To Muscle A Full Running Shark, You Get That Line In Your Hands And You Can Kiss It GOODBYE...If Your Lucky.
Three: PRACTACE...PRACTACE...PRACTACE!!! 
Would a 10/0 spooled with 80lb mono be a good back up for a 16/0 spooled with 130 dacron? Or would it be better to use the same strength line on the back up?
Yes As Long As Your Knot Is Firm Enough
Would a 10/0 spooled with 80lb mono be a good back up for a 16/0 spooled with 130 dacron? Or would it be better to use the same strength line on the back up?
Yes As Long As Your Knot Is Firm Enough
Even Though I Would Never Use 80lb to Dacron...With All Dacron You Dont Need Mono Line
What do you mean I dont need mono if I use dacron?
Dacron Is Tough Enough
Ya but my 10/0 (back up reel had only mono already so would it madder?
No... I've Only Seen Dacron Used Way Back In The 80's,...Rene Went After Big Mo At Bieaha Honda And Still Got Striped! Almost Went Over The Bridge!!!
So dacron is not good? You would prefer bullbuster or ande mono?
No Listen To Me...Dacron Is Nylon Line, Very Tough, Doesnt Stretch, Very Durable,...Its Good Line, But I Know That Its Very Expensive To Buy, And It Is Like A Cord (Diameter),...You Get Straight Up & Down On A Bridge In The Keys With Dacron And You Have To Be Very Careful With It Because It WONT STRETCH. Mear Body Weight Of The Shark Can Pull You Around With Dacron, So If You Want Keep the Dacron And Add Mono, Me Personally I Go With Straight Mono.