old sgm
You have not been following the Euro Smart Web sites.. and we have many posts here on it.... no sweat the site is a lot to absorb and some of it hard to find too
There are already 3 to 5 adapters the bolt circle of 112.5mm is maintained to allow use of Mercedes wheels. The adapters can be sourced in different widths I think from 25 to 45mm
They are specifically not allowed by Smart for safety reasons...
I am thinking a different angle... why not just drill the hub for 5x 112.5mm and tap for the correct thread? Any good machine shop can properly index the holes... rotors and drums will need to be done too