The issue with flight control wads and ported chokes is not so much about the hardness of the shot as it is about the fins on the wad. Those fins are turned backwards and face forward as the wad travels down the barrel. Only after exiting the barrel do they flip around to face to the rear. In a ported choke, the ends of those fins pointed forward lodge in the ports striking them with quite a lot of force and causing a lot of stress. This combined with the inability of the shot to compress creates a lot of pressure. At a minimum it tears the ends of the fins up causing them not to function as designed. You may well get a good pattern anyway as your stripping the wad like a conventional wad would be stripped in a ported choke, but the wad isn't performing as intended. At worst case, there is fear it may cause some ported chokes to crack.
As far a KICKS historically saying not to shoot Hevi in their chokes, it could be that the size and distribution of the ports leaves less metal between the ports. They are made of the same quality steel as most all chokes. Then again it could be insurance liability reasons or who knows what that has caused them to take that stance in the past. For a while they were saying Win XRHD was OK but Hevi was not. I read somewhere that that may have been because Win used a thicker, better quality wad. Fact is I know of many people who shoot HTL in conventional wads in KICKS chokes and never heard of an incident.
