Thanks Armin,
Worked like a charm, would be very useful if there would a way in the future to control it via the Thumb\Element grid visual interface...
I've also implemented it for Element Grid:
.elements-collection-region .ph{
padding-bottom: 100%!important;
}
.elements-collection-region .element-wrap img,
.elements-collection-region .element-wrap video{
width: 100% !important;
height: 100% !important;
object-fit: cover !important;
object-position: center !important;
}