Trying to to stretch line and get the most use out of it these days. Can I get away with keeping my older 6lb test flouro as a base for my spinning reel and tying on a slightly heavier 7lb test flouro on as my working line?

I cut down the older 6lb line to make up about 15% of my total as my base. Then filled the top 85% with the new 7lb test flouro line.  I’ve got it tied on to a solid leader knot which is buried deep in the spool.
I know that it’s not usually, or maybe ever practical to tie on a leader that’s heavier than the line behind it, but in this case the base line will never get close to touching air, or even seeing sunlight.  

 

With that being said, I still want to present the issue to everyone here because I don’t want to end up wasting more line by doing this… if it ends up causing me issues with casting distance? or my line to just break? Would it be safer for me to go ahead and take this base/leader line off and string only the 7lb on it?   
Of course I should of asked this question before I even spooled it…better now than never I guess 🙂. Thanks everyone!

The idea of backing is that its buried deep enough that you should never get to it by casting. If you cast your farthest and you are getting into the backing, then yes, replace it. If you are not, then you should be fine.

You’re good - should be no issues 

55 minutes ago, ZoomFluke said:

know that it’s not usually, or maybe ever practical to tie on a leader that’s heavier than the line behind it,

Dunno where you heard that - I use cheap 4# mono to back all my spinning rigs...whether the mainline is 8# FC, 6# Mono or 15# Braid...they all get the same backing.