Oso M
Step 14, page 10: Glue the 1/8" x 3/8" x 42" basswood bottom aft spar in place, being careful to keep the ribs straight over the plans.
There should be a top aft spar and a bottom aft spar...
… The wing construction instructions leave a lot to be desired, as you have to go over steps multiple times for each wing and backtrack. Its quite easy to lose your spot.
OS GT33 is my engine of choice as well..
more pictures shortly, I'm trying to finish getting things covered. Wings 90% done, body details need to be buttoned up.