I think the magnet height may have something to do with it ,I matched the 120 module to the 160 with the spacers and without the spacers and the 120 still fitted well in the magnets unlike the 140 which in the photo (second from the end)shows very slim magnets, about half the height which explains the spacers for that one, and so maybe on the bigger blocks they lifted the module to keep it cooler and centred on the magnets but this is only an idea.
Good to keep this open and if I find something I will post it.
