Well, these turn out to be a pretty simple model.

I'll need a guinea pig - if someone with a C3 could drop me a line with an address I'll post the prototype out FOC just to confirm the hole spacing on the back - as soon as I've heard that the fit is good I can batch print a load and start posting them out.
I've tested the Quad Lock mount on two different mounts and it's good - just need to confirm that it fits the C3 nicely.

I'll need a guinea pig - if someone with a C3 could drop me a line with an address I'll post the prototype out FOC just to confirm the hole spacing on the back - as soon as I've heard that the fit is good I can batch print a load and start posting them out.
I've tested the Quad Lock mount on two different mounts and it's good - just need to confirm that it fits the C3 nicely.