Two big successes today:
1. With the help of a dab of Gorilla glue that dried for 21 hours, an X-Acto knife, and some small screwdrivers, I managed to spread the cotter pin on the throttle arm. Then I checked all the other connections in the quadrant, and pronounced them satisfactory. I am done with that major project!
(The first photo below is the pile of tools I used to install the throttle quadrant!)
2. After last night's aborted attempts to get the flap switch panel installed, it finally succumbed to my efforts and slid into position. I installed the final low-profile black Allen-head screws, and gave it a test run. I must say that the position of this switch is absolutely perfect. You can reach it very easily, regardless of the position of the throttle, and it's actually super-convenient to use without looking or fumbling for it. It's actually better than I ever hoped!