I use Goya Quads 116 and 96, having 90 kg.
20 liters is perfect for me. First i was affraid about the 116 Liters, but you don't feel them once on a wave. Just perfect.
Overlap is huge 5.7 and 5.0, even gusty 4.5, no problem with the 116.
Just use Twinsers in the flat/smallish waves, really makes a difference (me 18.5 K4 rockets).
Alex

Another option you could consider is to allow yourself to have two boards with different design characteristics. This is what I have gone for and I am very pleased with my current set up. I have been trying to find this for at least 15 years... So, I have gone for the following two boards:

- One 83 litre tri/quad (222 long, 58 wide) with more rocker and fully dedicated to proper wave sailing. Control and turning ability is key in this board.
- One 95 litre tri/quad (226 long, 60.5 wide) with a faster rocker, but with a bit of tail kick. Still a full on wave board, but more all-round in character, fairly quick and easy to get going. Mobility is very important for me in this board.

The 83 litre board is aimed for proper wave sailing when there is more size to the swell and decent cross-on to side-off. Or just properly windy. This is used with 3.7 to 5.3, sweet size is powered 4.7. Board is sailed both as tri and quad. It does this really well, even if I need more sessions on it to really give the full review. This board size is perfect for me when proper wave sailing conditions are at hand.

The 95 litre board was a very good decision to get. It already is one of my all time favs. Thanks to the faster rocker, it allowed me to go down slightly in size for my "big" wave board (from 100 litres / 64 wide) without losing hardly any light wind performance but gaining quite a bit when it comes to turning ability. Even if I still like my 100 litre board very much, I must admit that it has hardly seen the water since I got my 95... I almost exclusively use this board in tri fin mode with assy front fins. Also, with the faster rocker, I can easily see this board as quite good in a spot with more current and slightly messy conditions. What I like the most about this board is how incredibly allround it is and still offers proper wave sailing ability. I use it with 5.7 to well powered 4.2 (which was a bit of a pleasant surprise). My fav sail on it is a three batten 5.0 in float n ride or just nicely powered conditions.

For a long time, my two wave boards have grown closer and closer in size, and I am now a strong believer in this solution. With the much improved upper wind range that 80 litre+ multifins offer combined with the approved turning ability that 95 litre+ faster rockered multi-fins are able to deliver, it really works very nicely for me. One of the things I really like doing is to just switch boards depending on conditions. Very gusty and shifty 4.7? 95 litres. Wind and waves picking up? Change to 83. Bigger waves and solid 5.3? 83. Declining winds? Change to 95.

I have tried some bigger wave boards and even if they quite often turn surprisingly good, many times I feel that they 'just' add size (to me, at my weight and level of sailing, that is) and not that much of a performance improvement as you could perhaps expect from going up 20-25 litre in size. I feel that the 105-110 litre+ proper wave boards are many times aimed at sailors over 90 kgs or so in weight, rather than giving 75-85 kg sailors more light wind performance. The one thing that can change this conclusion is if you have access to spots that allow proper ground swell sailing in very light, but fairly stable, winds. Then, I could easily see myself falling in love with a compact 120 litre quad/twin all the way up to 68-70 in width.

I am 79-80 kilos and fairly good at staying off the pie diet. I predominantly sail in the Nordics and Europe (Ireland, Portugal).