I don't, but I've seen Alex Tyrrell use a WFL09S with a D850 and Franck Fogarolo use an MWL-1 with a D500, both on a flip mount, every blackwater dive. Alex Mustard also recommends the MWL-1. The idea is, I believe, to have a real wide-angle solution for the chance that something quite big shows up, like a female blanket octopus - those grow up to a couple meters in length.I haven't. Almost five pounds!--Are you using it? I'd think that for blackwater, the ultrawide FOV wouldn't be helpful, because even the big things are pretty small, and the small things are tiny. (p.s.--I tried the link to your IG but it wouldn't load)
Re: IG link - weird, I just tried it and it works for me, both on desktop and on mobile.