Oh, and the raster-layer height, or Z size, is just the distance between the bottom and top planes of the raster-layer. It does not include the Z origin of the layer. To calculate the height of a carve, assuming your canvas Z size is identical to your workpiece thickness, you should be able to just add the layer's Z origin to its Z size to get the Z of the top plane of the layer, which is equal to the distance from the bottom of the canvas to the top of the layer.
- Charlie