Effective Fish Fighting Range with 5X Tippet

How much line has anyone here ever had off their reel while using a
5x or 6x tippet and ended up successfully landing a fish?

The reason I am askingis that I just got done switching lines around
from one small reel to another. I went out in the front yard and
stripped off all the line (AirFlo 3/4 Delta Taper) and backing (30lb
test Greenspot [its all I had on hand when I put it on the original
reel]). I came up with about 75' of backing plus the 90' of flyline. I
was a little taken aback by the apparent paucity of backing when the
thought occured to me that since this particular rod is rarely hooked
up to a leader that tests more than 4lb. (5x) what would be the
effective maximum amount of line and backing that could be removed by
a fish until the weight and drag of the line itself would cause the
tippet to part. So what do you think. I know rod action would have a
lot to do with it but it seems to me that there must rapidly come a
time with light tippets when any extra backing becomes superfluous.


g.c.