Hi Will, thanks for all the info, makes it easier to advise.
So in our last few Quad and Grip ranges we always tried to have a "perfect" 80-82L" board as the best allrounder, for riders of 75-85kg, not easy as 10kg makes quite a difference re the volume you need. Our best seller Grip 82 from 2019 was so well liked, but just a bit too small for 85kg riders. So we decided to make a "bigger" version of the 82 which is the new Grip 86, very similar outline, only a touch wider but we added thickness/volume to the board. So you have the extra flotation in the centre, but the rail shape and outline still feels like a small board. This is my go to board for 5.0/5.3 sailing when the wind is gusty, I normally ride the Grip 82 as my favourite allrounder.
So seems clear to me that you would be better off with the Grip 86, as the gap is quite large from 92 to 77 Stubby. Saying that, the 92 is also an amazing board, we made it a touch bigger than the 2019 Grip 89, to have better spacing with 82/86/92/102. If you were happy with that one, you could also take the 92, but you are fairly light, so not sure you need such a big board/sounds like you have to deal with a lot of bigger gusts, so maybe the 86 is the better choice.
Either of those will be fine, if you plan to also use it with a 5.3 or even a 5.7, for sure the 92 will have better bigger sail ability. If 5.0 is the biggest, then I think the 86 is the one. I have a bunch of friends who have all had the 82, they got the 86 as their light wind boards and are totally stoked to have the very similar feel, but with the extra volume. So can´t go wrong on that one. Good luck!