Down thrust and right thrust
 

How does one determine the degree of down thrust and right thrust for different airplanes?

3 and 3 is pretty common.

Sometimes you will find a plane that needs more or less down thrust after you fly it some. if a plane really clims abruptly with added power ..might need down thrust. If you throttle up and it drops .. probably too much down. I had this in a GeeBee R2.. wow was it interesting the first flight.. everytime I would throttle up to go around on a landing attempt it would nearly do a touch and go at speed when I didn't want it too !

Some will tell you you don't need any thrust at the firewall. But most kits I built for the last twenty five years used it.