Avro main spars
I don't anyone needs to worry too much about Shack main spars. It's essentially the same wing as on the Lancaster/Lincoln and fifty-odd years ago when I was a wet-behind-the-ears radar mech on a Lincoln squadron there was a panic that all aircraft were going to have to be grounded as a crack had been found in one of the mainspars. Then up popped a Corporal from Eng. Records with STI 7/1947 that stated that cracks in mainspars were OK as long as they were no longer than four and a half inched and stop-drilled