At the moment you can just set the Layer Depth at the main settings for all products.
This means, if the customer uploads his picture to the canvas it is for all products on the same layer depth.
But I need to set the layer depth different for some products. For example for an T-Shirt I need the Layer Depth standard (-1) at front, but for an mobile-phone-cover I don't use the base layer, just the shadow layer and the picture hast to go to layer depth 0 (zero), because I want the picture from the user behind the shadow layer, so he can see the shadow.
Please see attached PDF's
Hope you can realize this feature.