Re: leader/tippet length for trout
I read somewhere (sorry I cannot state the source) that the general length for a leader and tippet is somewhere around one to one and a half the length of the rod. That would expect why one would see tapered knotless leaders packaged in mostly 7.5' and 9' lengths. From there, the length of the leader can be adjusted for the factors that Raindogt stated.
For a five foot rod, I'd buy a 7.5' leader and tie some tippet on and call it good.