Not crappy info. I wasn't able to install a mark 2A into a mark 4 head case so in my personal experience that happened just last week, it wouldn't work. The chassis are the same width but the mark 4 holes sit further in from the sides. The rack kit that the mark 2 has on it has holes for both sizes so works with any of them. I have pictures showing the differences, I'll try to get links to them.