Hi matt,
i personally wouldnt put any wood thicker than 6 millimeters, i am a floor layer and i use 6 mill ply all the time because it doesnt follow sub floor (if its uneven) you could cut some strips and put them in the grooves first and then overlay with main sheets if you want to be really fussy!.........and also its not so thick that you have a issue finishing at the door edge,trims etc,..........also take all the interior out, you will get a much nicer finish than trying to cut round units, especially if you havent done this before, added bonus is that it will help keep your flooring in place,(im not familiar with madmatz stuff dont know if its glued down or not, if so ignore my last comment)..........ive just put some karndean oak effect tiles in mine looks bloody lovely if i dont say so my self,
good luck,.... hope this helps........................kev