Joylove, it would have to be the mount. If you notice the pics by the OP, the mirror mounts in the ceiling behind the windshield. You don't have a ceiling in a convertible. Hope this helps.

Revising this thread! I found a killer deal homelink/auto-dim for my '05 MCS R53! Great detailed instructions found here!

I've dissected a homelink mirror, a standard mirror and even installed an '08 into a '06 as well as the glass with compass in my '05. (My '05 MCS has the compass )
I can assist with questions!

I'll go first! Dude! Where's the photo DIY?!

^^^
This.......please educate us that's another mod that I wasn't planning on doing lol

I didn't expect to start any modification, or even split the mirror open, but here are some highlights:
I removed the compass/glass from an '08, removed the 315mhz module as well and installed the '05 one. Moved a self dimming glass into a non self dimming mirror (wife's MINI), still have to wire it, although she doesn't even notice, the glass has a good tint.
I took a few notes, but didn't take pictures. I still have parts, including the home link module from a mirror, a 07+ 315mhz module for the remote, glass and frame. I can take and upload pictures you may want to see.

Yeah that would be cool for us to see. We're you able to just pop the mirror back in? Very cool mod

Everything fit in perfectly. It's too bad MINI (BMW) doesn't sell the parts individually, just as a set.
I left the **** on my wife's mirror in place, even though it is not used.
There is a ring that houses a ball and socket pint (which allows you to adjust the mirror when it's mounted) that (a) i didn't need to remove and (b) was impossible to reinstall. All the wiring harnesses can be pulled through that hole.
I will take pictures of the spares this evening.

I love the compass, too. The orange is the same as the gauges and no identifying square around it, (like some Toyota mirrors).
Being able to remove the 315Mhz module (for remote) may make it easy to install an aftermarket self dimming. I actually have one that was selling, from a Infinity Q37x.

Great Post. It appears my universal remote board might have become inop after the mirror got wet. Did it appear that the board could be swapped out or repaired assuming one of the mirrors you had included that function? I hate to purchase a complete mirror just for the remote function.

Sorry to bring this back from the dead, trying to install my auto-dim/homelink mirror, and had to remove the plug housing to swap mirror bases, and seem to have forgotten which wire/pin goes in which pin housing (1-10). Can someone take a pic of theirs? Been searching for hours...