Trimmed off about 25mm of excess skin at the trailing edge of the rear top skin to match up with the plans. Then I took two pieces of posterboard, lined them up with the trailing edge of the rear top skin and pushed clecoes through them into the existing rivet holes along the rear bulkhead and longeron to secure them.
Next I removed the top skin and reattached the horizontal stabilizer and began the process of trimming the two posterboard templates to fit the curve of the stabilizer's leading edge. Ran out of time before finishing, but made good progess with the right side before heading off to work. When both sides are finished, I'll attach the posterboard to the rear top skin and trace out the cutouts and snip them out.
Posterboard templates attached to rear bulkhead
Another view of the templates.
Beginning to trim the templates to fit the horizontal stabilizer.