I ended up putting 2-3 degrees right thrust in my second SSE. But I'm putting the cart in front of the horse.

I built my (2nd) SSE true to the instruction manual. I flight trimmed the plane (OS 46 AX) and it was fun but inconsistent. I then started following Dean Pappas' trimming suggestions (Trimming Ground Up). I sealed the control surface hinge lines. Helped significantly. Still pulled a bit to the left. I then added 2-3 degrees right thrust. My take offs are as long and straight as I want to make them. My vertical up lines at full throttle are dead straight.

The technique that I used to add right thrust was, with a 12.25x3.75 prop mounted and positioned level, measure the distance from each tip to the end of the fuse at the fin/fuse junction. 3/16" is equivalent to one degree (source is Dean's Trimming Ground Up #2). I have about 3/8" difference and used washers between the engine mount and the firewall.

TTFN,