Displaying several images, overlay another group of images using transparency

I have effectively shown a single image and overlaid another one using 'Alphadata'. This is with 2D matrices. This 2D matrices are actually slices of a 3D image. I can show every slice of such 3D matrix at the same time using 'montage'. I would now like to display the all slices of a 3D matrix and overlay the slices of another matrix of the same size, giving it transparency properties. Basically, combining the two aforementioned actions. I asked how to do this using montage previously but since I got no answer I take it 'montage' is not the way to go? Are there any other methods I could try to accomplish this? I also tried displaying all the images as subplots but that proved to be inefficient and didn't look good.

I hope someone can help.

Thank you