Take out the middle fin, if you wanna be doing shortboard tricks like 360's or sliding out the tail when cutting back.
Alley Oops.. hmm if you dont call that advanced, I dont wanna know what you think is
I practise these kinda things .. pretty much all through my surfing career, and still havent quite mastered air 360's ... since they are an bugger to try land.
Its also not quite a question of pratice, but you need good waves to pull it off too.
I wouldnt advise using a 6'10 though, my personal opinion is anything around a 6'2 to a 6'4. I seriously doubt that thing of yours will lift off the water :p
Those fins are just fine, and i doubt seriously that you will notice any difference between them and standard sized fins.