We have large Chantecler roosters, easily 8 lbs each, and both bantam EEs and Belgian d 'Uccles, and sometimes one of the Chanties will mate with a bantam. Sometimes one of the EE roosters will try a standard hen, and in both cases, fertilization hasn't happened. Nobody has been injured either, all good.
Silkies are in another category, being both small, and fragile compared to so many other breeds, so often people keep their Silkie flock separate.
It really is dependent on the individuals involved, and space available.
Mary