what also helps a little is sailing overpowered and set the sail little bit flat, and as you push the fin a bit more open the sail slightly more compare to sailing downwind...
You will notice as soon as a gust comes and you will get overpowered and the sail will be slightly more opened it throws you upwind a lot.
Small analogy...imagenine sailing really overpowered like downwind speed sailing...when you look at the riders what happen when the stand more upright and open the sail a lot (almost holding the boom only with one hand) --> they go with a lot of speed upwind.
Ps: the analogy is too ridical but gives some ideas what works for upwind sailing.
PA 86 & eVo 100 (with S-1); iS 101 & 122 & 144 (with Overdrive)