Well, I'll try to take pictures as I go, if it works out well I'll post them. If it doesn't work as I expect, I'll just bury the pictures and you'll never hear about it again.
I think the exact placement of the magnet or magnets will depend on the layout in an individual locomotive. The one I'm converting happens to be an MTH with PS-1, and there's no chuff provision. On the good side, I get lots of smoke from the smoke unit, so it bodes well for a conversion. I'm also faced with the issue of having to provide a separate chuff switch for the RailSounds board, so I may have to get creative there, perhaps a SPDT relay to provide isolated contacts for the two purposes. Decisions...decisions...decisions...