tc,
I am guessing that the doors will not restrict CAT A due to any structural reasons, but rather from excess drag causing reduced climb and acceleration performance. For example, the BK117 actually reduces it's climb performance by a staggering 250 ft per minute for doors open, so if you are heavy and OEI, taking 250 fpm off you is likely to be severley embarassing, and thus its a good thing to remember for rescue crews who have a donk failure: close the doors as quick as you can!