Little doors! I've been building inspection hatches. 4 so far, with a few to go.
Two are on the wing roots, near the trailing edge, to access the fuel quick-release attachments. Top of the wing to access where the fuel return hits the tank, and lastly bottom of the elevator to access the trim tab servo.
I found the rest of the aluminium piano hinge I used for the doors, so I figured the easiest and lightest way to do the hatches is hinge at the upwind end and single nutplate at the downwind.