The adjacent sill section, fortunately in very good condition

The repair panels are considerably bigger than the amount I have cut off the old panel, only cut out the minimum to get to sound metal. The higher you go, the more work you will have to do to make the join invisible.

Wing fittings: In the above picture you can just about make out three spire clips along the bottom edge of the sill, for the wing lower-edge screws. Wing fitting kits are very variable in what they contain, some only conventional nuts, washers and bolts. There are three elongated washers AFH2546 for the lower edge of the wing as shown here, although there is an opinion that these should be between the wing and the sill for drainage and ventilation: (John Keene)

There should be two larger elongated washers AFH2627 for the upper rear wing bolts as shown here:

And this clamp plate AHH8094 (GT only) where the wing attaches to the A-post:

Both the above from mgb-gt.co.uk