It started off like the photos in my earlier thread.
Then I separated the diptstick part from the actual lid and it looked like this:


Looks like it was just glued in with a few dollops of glue. It also looks like the glue on the outer circle are what is keeping the silver bit of the cap to the black bit so I was careful not to make the whole thing fall apart.
Next job was to get rid of all the prongs sticking out.
I got them this far by hand:

Next I need to get the dremmel out and grind them all right back and also remove the parts that are recessed into the handle.
Then the next bit would be to cut the top off the original cap. I didn't want to do this to the original one just in case it wasn't a success. So I ordered a new one. Once that turns up I can cut the top off and size it up with the R8 cap.
I'm not even sure the cut-out in my carbon cover in the engine bay is big enough for this lid to pass through. I just had a thought, I could check the size against the original cover as I still have it in the garage (the fluid reservoir doesn't allow me to lower it enough to check the opening in situ).
And as described in my stereo modding thread I have removed the number plate light / lock assembly for a little research. More details in my stereo modding thread.
