Consider fabricating an inside-the-cockpit, front seat only -- lock
or damper.
Something you would see getting in.
Rear cockpit control locks WILL be overlooked.
Bungee cords work well to dampen the movement and might fold up
nicely.
Decorate with red ribbons.
Add control lock item(s) to pre-flight and post-flight checklists.

(Google "Checklist Boeing B-17" for a reason to create / use pre-
flight checklists.)