I will only recommend going straight braid if and only if you are fishing from a floating device. This is also a real NO (for me) if you are fishing from the shore.
Many here giving advice probably fish from a boat and so their advice is good.
However, if you are fishing from the shore, I would consider going with mono straight up or mono with your fc leader.
Here is why:
1) Even at 15# strength, braid will be very difficult for you to break off. Even if you managed to break the line, there is now a strand of braid floating around for nearly forever in the river because it will hardly break down.
Another question - how is your catch rate compared to your friends? About the same, better, or worse? If it ain’t broke, don’t try to fix it. The grass isn’t always greener on the other side.
I am only talking about straight braid that wouldn’t recommend if you’re shorebound.
A 4000 size also holds a heck of a line of line so if you decide to use braid so I recommend the advice already given about putting a mono backing, then the rest braid until your leader.
One last thing. FC sinks so if you’re fishing poppers and you see a worsening in performance, just switch to a mono leader.
Oops. One more thing. I recommend the alright knot to join all your lines. It is a great knot and can be used even when the diameters of the lines to be joined vary greatly in diameter.
Personally, I’d stick with the 8# mono and add an 8-10# leader if you “really” have to use or want to try fc.