fiberglass cracks

Turbo Diesel Dude wrote:
You can "stop drill" at the end of the cracks and repair with epoxy. Old aircraft metal smiths trick of which I was not, but a good buddy was.

Retired from an aircraft company after 30 years this is good advice for aluminum skins. In addition to drilling a hole several layers of fiber glass cloth and epoxy on the backside or front side will reinforce the area to prevent further cracking. Square corners produce stress risers or areas to concentrate stress that is in the outside skin and causes these cracks.