I have a tenor Fluke in A6 tuning, i.e., a minor-3rd down from GCEA for anything I do vocally.
Specifically E4-A3-C#4-F#4.
I am using the Martin M620 strings, and if this tuning is your target, with a brand NEW set of M620s, you NEVER tune beyond, otherwise the strings will be stretched too far and sound like rubber bands if first settled and stretched to C6 or Bb tuning...
I dont care to transpose and play the C6 chord shapes. I never sing in group settings, and if I am going to record myself and play other instruments in multi-tracking, for some things I might transpose, like for playing bass which is pretty easy, or otherwise use a software pitch-shifting plugin in my DAW program.
If I am playing in a group setting, I will use one of my other ukes that is tuned GCEA so I dont have to worry about it.
Yes, I am lazy. I want to make music, not endlessly gyrate the Circle of Fifths.
I've studied music my whole life since I am 7 yrs old (48 now), both in school and on my own, and really I am much more an auditory learner and player, and have only small reasons for bothering with documentation, and prefer to rely on my memory and keep my brain sharp by using it instead of a transposing slide-rule...
Also, if I want to use my Fluke in A6 tuning with a group, I can always just put a capo on the 3rd fret and !viola! C6 tuning