RE: FG and Smartech wheels
From what I know the dia is different.
Here is the data on a Carson/Smartech MT Rim.
Dia: 121mm (aprox 4.76" )
Widht: 80mm (aprox 3.15" )
The Carson/Smartech MT Rim has a steel reinforcement ring, but even with 17mm wheel squares there is only just room for Magura Hydro's
Unfortunately I only have the weak Carson/Smartech Rims.
From the pictures of the comming 4WD smartech/carson it looks like new and better rims are on the way.