The only reels i keep are cheap stuff (which i also play with), gosen and the like, so i just don't care so long as i don't come up short.
I measured my wingspan to be about 5.5 feet and go from there. I'll look up a pattern/length and adjust accordingly, but never use an actual tape/ruler or what have ya. Did that once and came up with my wingspan. I know about what a foot is if i need to adjust.
Individual sets are simple, especially since most are at least abit longer than advertised anyhow.