I am not giving up Annie, but I think this is going to be something that will require some testing and fiddling which I rather not do at the moment.
I am sure later I will get back to it, as it sounds to be an interesting experiment.
Ole, I think on E bay US there is a guy selling rhodium. If not, contact chrristian Nzè he is using rhodium and Iridium to experiment in making coatings a la pt/pd. I will tery to get you his e mail address.
BTW Annie, if you want to try an experiment and are unsure, post it here! I will be glad to help you and I am sure others will also.