I'm going on with some tests.
What I've done now is to use OpenLayers asking for a single image, insted of tiles.
In this case, of course, we have no problem with styled areas, but we have a very strange problem: when you zoom in and out, the layers shift. but this happens only if the browser window is "big" (I do not know exactly how big, It seems over 1300 px) and the more it is big the more you have a big offset ... very strange, also to explain...
I did two videos:
Here openlayers asks for tiles -> problem with styled areas
Here openlayers asks for single image -> problem with shifting layers
Hope you have some helpfull suggestions.
Thanks in advange