I am a regular on LH400/404 and 401/405 and occasionally on LH446/447 (all North Atlantic routes--FRA-JFK and FRA-DEN for those not familiar), and I have never been charged (either in C or in M class) to take my (2 pair sized) ski bag, which, when padded with extra clothing and such to protect the skis (as suggested very wisely by sperrgepaeck), clearly exceeds the piece size for normal baggage allowance.
Having said that, it seems, by the policy as written, I could be charged. I am an LH *G, but there is nothing in the current policy that seems to entitle me to a free ski bag when it exceeds my normal *G baggage allowance, which allows for heavier bags, but not larger ones. I wonder if I am charged sometime in the future for my ski bag, can I do anything about it, and should I be upset? :-)