My last rectifier-fitted disc holder disappeared onto the tarmac a couple of weeks ago and on BHM's advice today I screwed the replacement to the forward nearside allen key bolt holding the leather coaming cover. Seems the perfect site - the cockpit vibrates much less than the engine mounts so I expect this to survive. A bit longer, anyhoo. Just about legal too, at least more than the rectifier position.
Notlob