I asked this question a while back and never found the answer to this question, but now I have an answer. I got to go with my buddy to the range a few weeks ago- and to my surprise, the magazine fed fine with his Shadow 2 kadet kit on my 75B's frame. HOWEVER- here is the caveat. Due to the different follower design, the red follower on the Kadet II magazine doesn't lock the slide back on the last round. But in the several mags I fired, I had no issues other than the slide not locking back on the last round. Just something I thought I'd post my experience here.