[kyrilliondaemon]

50 by 40cm is what I read... So I don't get what you mean there. I was assuming its wider than tall but I may be wrong...
Either way, twice 40 by 50, is 80 by 50 total. The bin is smaller so its less.
Plus loads of small modules really don't add up to a single big one. Like Scamps rotastak adds to her total cage space, but without the bin (about 6000 alone) it didn't matter how much she had because it wasn't enough. Two big-ish modules do add up to a good cage, but multiple small ones don't.

You might be ok, but if the bin is less than 40 by 50 at the base then its still below the minimum size. If its smaller than the peggy then it is less, and therefore is less than ideal.