Hi, I just did this exact thing with a V-Stoptail G5260 (got as a preorder). I bought the Gretsch with this intention and after a little tinkering it seems excellent for the Bass VI way of life!
The most important thing is adequate string tension to minimize low E flop-and-slop. I essentially bought short scale bass strings that were supposed to have smaller string ball ends.
Sidenote on V-Stoptail vs Bigsby---a Bigsby might pose two problems reasons: (1) possible added string length such that short scale bass strings wouldn't work (not sure about that, but it sounds like it makes sense); (2) tuning issues with a Bigsby b/c they utilize a standard saddle set instead of roller saddles. Also, the Bigsby is technically a licensed knock-off (although what's the diff really, and does that even matter?).
Anyway, to make it work, you need the right strings. I've heard other people go for more expensive sets, but I did a bit of research and bought two Bass VI-type sets that were like $12 and $15, respectively. (1) Ernie Ball 6 string bass slinky (Custom Gauge 2837)---20, 30, 42, 54, 74, 90; and (2) D-Addario EXL156---23, 34, 44, 56, 72, 84.
I tried the D'Addario set b/c strings 1-3 were thicker. Worked well. Sounds great! Especially with the bridge pickup on those 1-3 strings. Wow! But sadly, I got the urge/feeling that I need a different amp to handle the low frequencies better
Tuning was stable after getting everything set up and I had to raise the bridge a little on the 4-6 strings because of low E floppiness.
My only critique is that the 84 is a little sloppy. The only thing I would change is to get a thicker gauge on 4-6 strings, or at least a 90 on the low E. I've read accounts of other people preferring that and going higher. 90 and higher will require some nut slot adjustment, but if you have a plastic or "synthetic bone" cheapo nut, you can just kind of use the thicker string to make itself room (do this gingerly---no sane person would recommend this). It's possible 95 would require widening the tuning peg and the V-Stoptail low E string hole.
The other big thing was that I had to use a file to make the V-Stoptail piece low E string hole bigger because the ball end of the low E string included some slightly thicker windings (mm's). Wasn't hard though.
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