On 6-string, I'd go A C# E F# A C#, which I sometimes find somewhat lacking in the high end. But I want the low root somewhere. So I usually go C6 = C E G A C E. If I use a 6-string at all, which is not often. I definitely prefer 8 strings for 6th tunings, period. F# A C# E F# A C# E is my go-to for A6.On 6 strings, I haven't really liked A6 (or C6) because there is no bottom end. But the 8 string version, F# A C# E F# A C# E looks really good. You get that F#m7 going on two full octaves. Do most A6 players use 8 strings?
One exception is this National Silvo - viewtopic.php?t=352985 - which I tune nominally to G6 = E G B D E G. I sometimes sharpen the low G for G6/E7, or you could call it E7#9; or also sharp the high G for just a plain E7, or flatten it to F# for E9. Pretty heavy strings, and it gets a bit of electric resonator vibe. I like it for blues.
