Hi There,

We use metal frames on panels of about 3ftX4ft
and you can weld mash to it.

However for small sizes it is better to construct the backing and frame out of wood,like here:
http://truefresco.net/gallery/showgallery.php?cat=545&thumb=1

also for scratch coat you should use lime (you can use construction lime - or even simple factory bagged stucco mix) and about 10-15% of cement.