NW072 Single String : Acoustic 7 string

I use it on my acoustic 7 string as my low B as there's nothing else available of similar thickness. Elixir has a .59 which is not thick enough. I tune down my 7 string acoustic a a whole step down so my lowest note is concert A 55Hz. The string holds up ok with the low tuning, but I wish there was a .74 or even .76 as I can use a bit more tension. The rest of my strings are from Martin Retro 13s and the winding on my low E is quite larger than the winding on the .72 Daddario. The Martin definitely sounds bigger and brighter - the daddario sounds a bit muffled and weak in comparison. I wish Daddario would make a single .72 in NYXL or Martin made thicker Retro strings but I understand that this is very very niche so I use what I can find.