I'm 5'11" too and have had my SB130LR for about 3 months. It's a large and is a great fit for me. Previously I had a 2018 SB5LR and while it was the correct size for me, the SB130LR actually feels a better fit. It feels shorter surprisingly, even though the numbers would suggest otherwise.
I borrowed my brother's previous generation SB5 which was a medium prior to getting mine and it was obviously too small for me. I've since ridden his SB150 briefly and while it too is too small for me, it's not the same amount too small as his SB5 was.
I guess what I'm trying to say is, get a large. (Probably)