Pixel map staking

Hi all!

I'm new to pixel mapping so perhaps this is more a question of how pixel mapping in general works than a specific Hog 4 software question.
Anyway, the question is about having multiple layers of pixel maps.
In my design I have one plot with 6 5*5 cell matrices (comparable to the jarag-5 matrices).
In this plot I have 6 pixel maps covering each matrix individually and one covering all the matrices.
When I try to program the pixel map layer covering all matrices, the plot shows the correct pattern but when I try to program the individual matrices using a pixel map layer it doesn't show anything.
All pixel maps have separate layers by the way.
First of all, is what I want to do even possible? And if so, how can I make it work?

Thanks!