I don't mean to burst your bubble, but honestly there is nothing magical about a goniometer. It just gets you into the general neighborhood, and then you do the fine tuning by feel.

If your saddle feels too high, lower it a 1/8 inch or so at a time until it feels better and you still have that increased sense of power. Your saddle may end up in a position that puts your knee at 37 degrees or 43 degrees or even 40 degrees, it doesn't matter as long as you feel good and strong.

Put a mark on your seat post when you find the height that feels right. Then if it slips down, you know where to set it again.