Hi Birdmanpete - welcome to the forum. I had a D18 although I did not build the basic airframe - like many others I took over a partly completed project thinking it was 90% finished (more like 10%). The trim tab should be neutral when the fully-flying elevator is at rest, ie, stick forward - because the elevator is so large it tends to sit in a forward position. You will see what I mean once the cable to the elevator is in place. As the stick is pulled back and the elevator rises at the rear the trim tab is activated by the very clever arrangement in the plans (cant remember what it was called) . What engine are you planning to put in the D18? I have seen VW's, (underpowered), Subarus, (generally unreliable), Jabirus (ok, but they have had some issues) and Rotaxs. By far the best is the Rotax - either 912 or 912ULS. Best of luck with the build. If there is anything else I can help with, let me know.