Hi there, that is good info to work with - so I am 78kg´s, used to ride both the TriWave and Quad, depending on conditions. The 2018/19 Grip 82 is considerably better in planing than the previous Quad 82, in medium to powered condition fairly similar to the Triwave, which was a planing machine, especially underpowered. The second generation of the Grip range has only smaller adjustments on the 68/75/82 sizes, as these were really well accepted/liked/test favourites. But even these smaller changes really helped a lot to release the board in the top turn, which was the only weakness of the shape, a bit too much "grip" off the top.
The bigger sizes, including the 86, got a lot more work put into them and the feedback on the 86 in particular is very good from people over 80kg looking for one board solution. Even for me with sub 80kg, the 90/95L boards are a bit too big when the waves get choppier or much bigger - the 86 is an excellent choice as it´s not much wider than the 82, but the extra volume just makes it so much easier in the 5-0/5.3 conditions, especially when not planing. So I think you´ll be more than happy with the 86, the extra volume/size was conceived a ONE board solution for riders of 80+-90kg´s, so far everyone who has tried it is very stoked.
Your Quad does have quite a bit of rocker, had the tendency to ride "tail-up/nose down" in a straight line, this was really obvious when we were testing it vs the TriWave or Grip protos some years ago, I remember it pretty clearly, was also the reason I ended up mainly moving towards the Triwave - as the small gain in turning ability vs the TriWave, was not worth the extra effort to get planing, which the TriWave did so much better. And afterwards, when we had the Grip finally in production, I could travel/use just one 80L board, instead of having one for each type of condition, with the Grip actually keeping the speed better in turns anyway than the Quad.
Like anything, you may need a cpl of sessions to get used to the different feel of the Grip 86, vs your Quad, but I was blown away by the Grip when we first tested them three years ago, the testing over the last 2 years on the new generation was a similar "aha" experience, especially on the 86/92/102 sizes.
Interesting you mention the Stubby - Nik Baker, Ex World Cup Champion and since some years our UK Sales Agent, has been riding the Stubby´s the last few years. He got a bit heavier, 90kg´s, wrote me a what´sapp on the weekend that he just loves the Grip 86 in his local conditions in South Coast UK, still uses the Stubby sometimes, but says the Grip 86 covers basically all his needs?