Glued and clamped on the wingtip.

I learned that when you iron on covering it may bubble if there is air trapped in the underlying compartment so I drilled small holes in the ribs to allow air to escape. My covering skills are still evolving so I need all the help I can get

Bottom of the wing is sheeted. I clamped the curved sheet to make sure it would stay.
Popsicle sticks, tongue depressors, etc. are useful for helping clamp. I sometimes place wax paper under them to make sure they don't stick.