I've been doing fluorocarbon fishing line (technically "leader") on my ukuleles for almost 10 years. Throughout the number of threads on the subject, it is has been pretty much established that ukulele string manufacturers generally use fluorocarbon fishing line.
With the exception of Aquila, and possibly D'Aaddario, few have the financial wherewithal to develop a unique string formula and produce a run of various stings so they can be sold to a relatively small market in 5 foot increments. Some people loved Southcoast stings and Dirk had a unique list of sources to assemble his string sets. The rub has always been getting the right mix of manufactured strings.
The consensus has been that Seaguar, for the most part, is the best overall fishing leader to use.
I have found that it is really all about the diameter of the line within a manufacturer. For Seaguar, to figure out diameters, here is where you start:
http://worthc.to/english/w_strings.html
Using the Worth chart for diameters above will give you a good starting point. I primarily used Seaguar Blue Label and Premier. Premier is tournament line so it has to meet specific breaking specs and is probably made to closer tolerances.
The biggest difference I have found is that the Premier tends to stretch a bit more and the thinnest strings get a bit smaller in diameter than the Blue Label. I also have to be a little bit less aggressive on manually stretching the Premier.
Keep in mind that a tenor ukulele has and overall (total 4 strings) string tension of around 40 lbs and most fishing line used are at least 30lb per string. I don't care for Seaguar Red, but I have heard good things about Seaguar Pink, but haven't tried them yet.
I have 8-10 rolls of Seaguar that I will mix and match depending on the ukulele. Depending on the tuning and if the "C" string booms or thuds, I will with go with Premier .028" over Blue Label .029". There is a .024" in both Blue Label and Premier, I have not used the Blue Label variant. I have used digital calipers to measure the string diameters to Oasis and others.
An important note is that the Blue Label 50lb is really .026" not .028" as shown on the Seaguar website:
https://seaguar.com/saltwater
I have pretty much stopped the fishing line/leader paper chase and just tune each ukulele to the best sound (Bb, B, C) and am plsying more and tweaking less. Others can take up the charge.
John