Top: An old 'wedge' which despite being metal had one of the angled ends break away.
Middle: Plastic wedge which had completely broken up, albeit after very many years. Note the very shallow angled face compared to the top one.
Bottom: Fabricated steel wedge which should last for ever.
Fitted to plinth and door.
Mirror fitted, wedge length set so grub-screw is just fully seated into mirror base, maybe another few thou to just recess it wouldn't have hurt.
The 'flat' plinth is very slightly thicker at the lower edge compared to the upper, as well as being curved to fit the door skin:
The roadster has the mirrors further forwards than they should be as I used them and a plate inside the door to strengthen the skin after a Crack of Doom repair. As a result they obstruct full opening of the vents, but then they are rarely needed in a roadster:
Also the passenger side is slightly obscured by the drop-glass channel, but it has never been an issue in use:
If I did it again - or if the doors are ever repainted - then I would consider moving them forwards enough to allow the vents to open, which should still give some strengthening against the Crack of Doom.
The V8 - which I assume is factory standard - is as here:
Moss Europe have several different types of mirror available but the ones like mine have different components. Mine just have the flat plinth 'A', the piece that the mirror stem clamps onto 'B' and the screws. 'C' is an angled plinth perhaps needed where the door skin doesn't have the angled mounting face that the MGB has, but how that is used with 'D' and 'B' I don't know. Maybe 'D' fits in the skin holes in place of 'A' with 'C' covering it, but how 'B' fits on top of that I don't know, and long screws would be needed to go through all three: