Some pictures of the speaker install I talked about here. Sorry for the nasty digicam quality, it was too much work to go and find the tripod and the SLR. While I had the body off I took the opportunity to make a styrene bottom plate for the sound box to replace the blob of Blu-Tak which was filling that role in the Mk.1 version. It's still not a classy install, but it works and apart from cutting the hole is still reversible for when I find a better way.

Here are the main components. I've already removed the grille cover with the tip of a no. 11 blade here. If I was doing it again I'd be very careful to only exert pressure near the corners, since it's possible to create hairline cracks if you do it in the middle, and it might also give more chance of getting all the pips out rather than snapping them - I had two break. Not a big deal though.

Here's the grille drilled out, prior to cleaning up with a file. Take care and go slowly - lots of detail to spoil, as you can see from my errant knife blade leaving a mark towards the top of the bonnet.

I spliced the decoder and pickup wires together with soldered joints and tape. The motor terminals were easy to get to so I soldered directly to those. The rest of the decoder wires are bundled up in case I want to run lights later.

The speaker is mounted to the interior of the body using a shell with a thin skool sossage (chiz chiz chiz) of Blu-Tak. This needs to make a seal all the way around.

And finally here's the sound box with ugly Blu-Tak fillet to hopefully seal the enclosure. The back and bottom are made from 1mm styrene, with a groove in the back to clear the motor shaft. I cut the plates roughly to shape and then worked on them with sandpaper and files to get something close to the body shell's shape - the last 0.5mm gap is taken up with the Blu-Tak. Don't forget to plug the exhaust (I assume) outlet! I haven't sealed around the bottom plate yet in this picture.

I hope this is useful to anyone thinking about doing one of these. It wasn't that hard, it probably took a couple of hours, and I've only installed a couple of hard-wired motor-only decoders before. Admittedly one of those was in a Bachmann On30 Porter, which is not particularly easy. All that said, look to the more experienced folk (e.g. the DCC fitting guides in the forums) for how to do a proper job rather than my less professional version

The end result is fun, it's not super loud and there's some hiss from both the ESU mixer (I think) and some of the sound samples, but it compares well to some factory-fitted models I've tried. Howes should be congratulated on the driving qualities - the rev up, run, coast and stop all feel excellent. Now I want to do my EWS one