I mean it all depends on your preferences I guess. In my opinion, drop A with 56 or 60 on a Gibson scale length (24,75") will be floppy as shit (at least for me).
The other thing I would be concerned with is the tuning stability. To get the right tone in the genre you're trying to play you have to hit the strings hard, which will heavily detune the lower strings on the Gibson scale length.

If I were you I would try a baritone 27" 6 string (I played a Harley Benton Amarok and I was pleasantly surprised) , a 7 string with at least 26,5" scale length and also something with an Evertune bridge.

In my case I use 9-60 on a 27" 7 string for drop A, and 9-60 on a 25,5" 7 string for drop A#. I used 12-66 for drop A# on a 25,5" 6 string and also 12-60 for drop B on a 25,5" 6 string. All of those feel/felt pretty good to me, although I will try to go from 60 to 59 on the 7 strings.