RE: COMP ARF 110" F4U ARF WITH FOLDING WING ASSEMBLY
The leather cover or hinge can be made from an old pair of TIG welding gloves. They are very soft thin white or off white leather with a tan cuff that is heavier. I have 4 or 5 pair in my tool box awaiting a plane to install on. If you can't wait to wear out a pair of gloves just buy a pair at about $10 at the local welding supply store.
My original Ziroli Corsair front gear doors had a pair of removable pin hinges and I wound torsion springs for the doors out of about .012 wire as I recall. The doors had just a small block of wood that rode on the strut.
My installation was almost exactly as yours is with the filler blocks. I used a mechanical linkage operated by the gear leg to close the main doors. This was all done on CAD before eveyrone had CAD stuff. It all worked right out of the box and was very trouble free.