Sometimes you have to be creative in the way you fasten the units in. Sometimes the bolt holes on the bottom of the cabinet don't match the bolt holes in the bottom panel, but I've not yet been able to get one to remain fastened in.
I already have a cabinet for the X202B but it doesnt match the cabinet on my FM200B, when I get the matching cab I will take the other one and save it for the next project, I usually just slide them in and not worry about the bolt holes...