Well as you say there are some registered tetraploids from 'Europa' and some where the parent is just listed as H. fulva, so could be 'Europa', already. Maybe look them up in the NGA database, that might show how many people have them and thus whether there is much interest. I guess we don't know whether the ploidy has been confirmed as tetraploid for the already registered ones.
Just out of curiosity I tried 'Kwanso' pollen on 'Europa' this year on the basis that both are triploid. Not many because I only thought of it as bloom was winding down, but none that I tried took.
