instead of just removing the corner panel because it's rivetted on the outer side, back door being other side, if you remove the inner trim you will see a number of nuts i believe 10mm, undo all of these, it also has fixings in the inner arch, the actual top of the wing is stuck in place, careful when removing wing, you don't want to flex it too much, you may break the window, speaking from experience. :shock:
hope this helps. pegleg66