Make sure you are not oversheeting the main, even in 10 kts. of wind. The H16 has a definite upwind groove but it does take some practice to get it right.

19 y.o. sails will not help pointing.

This last item is difficult to describe in writing, it's kind of a feel thing: Your crew may be trapping too early and the boat is sailing too flat. Let the windward hull rise up and drive the leeward hull deeper to acheive better lift. I think this is especially true in moderate wind and flat water.