Part II.
This time we will use a knife to carve our way thru the plastic housing.
I choose my old and trusted Swiss Army Knife – I keep the small blade as sharp as possible.(If you have a better tool and/or a better way to make the hole – go ahead)
This is the things we will work with.

Align the micro switch where we want it positioned.

Mark the plastic housing with the knife.

Make the markings a bit deeper with the knife as we are going to carve our way down…

The plastic housing is actually kind of soft to carve in, be careful not to hurt your fingers or let the blade go past the marking.

Measure with the micro switch how wide the hole is going to be and to keep track of the alignment.
This is the result of 5 minutes work.

Start tracing straight lines along the housing, Measure with micro switch to verify alignment.

Carefully make the markings deeper by repeating the process, but with a bit more force.

Really soon you will break through the housing and it is really easy to overdo and get out of bounds.
Cut through the remaining line and start on the other side, when done cut diagonally.

With some force applied it is easy to bend down the scrap in the center.
Clean up the edges with the knife.

A bit more carving to do along the sides makes the hole nice and tidy.
Another measure – and this time the micro switch actually fits, almost.

Now it is in the desired position. Time for measuring again.

This time it fits up to the mounting brackets that are a little bit wider than the rest of the body, perfect in other means.

Carved a bit more..tested again

Now we are close

With a little bit more force I could get it into the hole but it has to be pushed down even further.

That is the desired position.

This is how it looks like from the rear. Inside we can barely see the micro switch.

And here from the front, the shiny parts are the plates to solder on.

Even more and big pictures can be found at this URL
http://undcon.com/mods/irpen/Questions and comments in this thread please:
http://www.wiimoteproject.com/index.php?topic=674.0In part III we will do the electronics.
//UndCon