Rudimentary medical knowledge but windpipes are fuckin strong, you'd definitely want to be aiming for more constriction of arteries or simple airflow block, so it shouldn't be *too* tight feeling for a more comfortable partial. I agree with the people saying SI sometimes just overrides partial, especially in the cases of windpipe crushing feeling.
In BDSM, (I promise this is relevant) the way to choke someone out without permanent damage is NOT thumbs compressing windpipe, it's actually firm grip on either side of the neck (higher up is better) to block the carotid arteries until your partner passes out. People have managed to hang themselves with all sorts of materials, but the important thing is making sure there is firm pressure on the sides of the neck, not just the front and center where your windpipe is strongest. If you're not sure with where that is for you, try simply firming holding the sides of your own neck until you find a spot that makes you lightheaded to hold for several seconds, and that would be the spot you want to aim for.
I don't plan on partial but I had an almost-successful one a few years ago with a simple electrical cable high up on the neck - the issue wasn't placement for me, it was trying while my roommate was still home. Whoops...