Yes, I am very much aware of the individualities of airframes. Follow Whirls' link and look at my argument on that discussion, which was in a nutshell that generalities are dangerous things to believe. In that instance one contributor was quite adamant that snow could not stick to an airframe - I disagreed. Icing trials, particularly on helicopters, need to be very carefully carried out for a meaningful icing clearance to be issued. Subsequent experience in a variety of conditions may result in a clearance being further restricted or eased.