Ah, CD Drives are pigs, as they say 5 1/4" although thats apparantly a measure of something else, not the bay, when I did my PC case DT project at school (which i can safely say failed miserably) it took me a long time to get teh mounts in the right place to hold them!
Very Original way of doing things and I really like the design, good luck! Im sure you will do better than I did!
Ruan