The front screen aperture wasn't quite as bad as the rear, but still required the rusty metal to be cut out & replaces with new steel.
New metal welded in:-
Once the new steel was totally seam welded, the repairs were then lead loaded & filed down to the right contours prior to priming. lead loading is a bit of a dying art these days, with people happy enough just to use body filler for their repairs. In the good old days, before filler was used extensively, lead or body solder was used to carry out repairs. The benefits of using lead are that it won't shrink (whereas filler could with time) or allow water to penetrate from behind, so a repair could last indefinitely without ever coming back to haunt you. The pics show the lead applied to the roof & then of it taking shape as it's filed down.
The lead being filed down & shaped.
Once the repairs were finished I gave it a coat of epoxy primer to protect it from the weather,