I'm looking at two different boards, both 5'11 but one 36L and one 31L. Do you think I'd notice a massive difference in this? I'm 5'10 and about 76kg.
This is just a guess but i'd say the difference would be around 5 litres.
Nothing wrong with your maths zen
Think about it in percentages, 36L is like about 15% more than 31L so expect it will float 15% more ...
Five litres of water....can last you days.....if rationed....
If you're looking at a fish or step-up go for 36L for your weight. If it's just a shorty 31L sounds closer to the mark. 36L will possibly feel like a boat in a shorty for you...
More litreage.....doesn't cost much.....be daring.........go a 39L....Twinny..