Dude - welcome to the game. It sounds like youve really got the bug, and that's cool. While I know my way around the front of a boat, I am a begginer-level skipper, too.

I have a small boardless boat also that sails very similarly to the H16. I'm guilty of often pinching unless I REALLY concentrate on how the boat is feeling. I always go past that 90-degree point until I need to almost look over my OTHER shoulder to see the upwind mark. I'd say this usually puts me in the 100-110 degree range. Assuming you have an accurate waypoint for your upwind mark, this would be when the VMG becomes a negative number after being zero for a few moments. I take a deep breath, focus on boatspeed, and make the best tack I can. I'd rather go a boatlength or two too far rather than rush it and have a bad tack.

I find beating upwind to be much more difficult than running, so this is where I need the most practice. Nothing feels better to me right now than getting upwind without a blown tack, stalling, and without drifting into the mark because I tried to pinch it off at the end of the leg.

Good luck!

ps - I have a hand-held GPS with an electronic compass. It has helped me a great deal. A lot of guys my age do better with anything in life that can be made to seem more like a video game.