thanks for the Quick replies, my next question is
(1) do I make the doubler for the flange long enough to pick up the rivet either side of the repair - as in the photo above or
(2) Just long enough to cover the repair ie only use the one skin rivet to hold the double in place or
(3) Drill new holes 1/2 inch either side of the repair and rivet doubler to flange before the skin goes on
note the hole spacing on the flange is about 1 1/4 "
... and of course the doubler goes on the inside
thanks again Bernie