the Nemesis wheel clamp - it won't fit my wheel!

Barefoot Wanderer

Hi, just bought a second hand nemesis wheel clamp and I can't get it to fit

my tyre is 145/80 R12 - so it is has 12 inch wheels - on their web site it states that this clamp is for any wheel which is 145mm (or above) wide and 10-20 inch wheels??

The problem I have is that when I fix the claw-clamp onto the wheel, there's not enough room to then attatch the face plate which covers the nuts, it just won't fit!

Has anyone else had this same problem with small wheels? Am I missing something? I just don't see a way it can fit. Plz help!