Just set it up by the lines.

Go fly it and go straight up. On the way up do not correct it for anything but make sure the wings are level before pulling up and do not change the power settings, just let it slow up. If the plane goes straight up without doing anything the engine thrust angles are correct and you do not need to change anything but this will not be likely. I have yet to see any plane that did not need adjustments.

If the plane goes to the left, add a washer on each bolt between the firewall and engine on the right side when facing the plane from the front
If the plane goes right, add a washer under each bolt between the firewall and engine on the left side when facing the plane from the front


Now fly it straight and level at about 1/2 throttle into the wind and suddenly chop the throttle, if the plane drops the nose suddenly add a washer to each bolt at the bottom between the firewall and engine. If the nose goes up suddenly add a washer to each top bolt between the firewall and engine. If the plane slowly drops the nose it's fine

The idea is to get the plane to track as straight as possible using the engine thrust angles. trying to set it up before hand is tricky at best because the engine torque, prop diameter and pitch all contribute to how it tracks in the air

As I said before, the lines are already setup for thrust based on the recommended engine/prop range. If you change that to a bigger engine/prop combo then you will have to make adjustments after you mount the engine and fly it

I typically spend 20 to 50 flights getting a plane properly trimmed. I have never seen a plane yet in any size that did not need some work. About the best one I have seen so far is my Comp-ARF 3.0m Extra 260. I set it up exactly like the book using exactly the recommended equipment including engine but a different prop and though I did not need a click of trim anywhere to fly straight and level, I did need one degree of right thrust because I used a different prop which caused the plane to pull ever so slightly to the left jsut as it started to slow going straight up