I am currently prepping some masonite with rabbit size and my own gesso made with rabbit skin size, zinc white and whitening. So far its looking really appealing, its got an extremely smooth, undisturbed surface. With enough sanding it gets like egg-shell. To me I prefer an inflexible surface with neutral texture. The idea that the ground is much less flexible and harder to disturb by punctures, bruises etcseems to make sense to help a paintings life-span. Also in the act of painting itself, sometimes its neccesary to scrub a recent layer off with turps etc, which flexes the canvas and in several years would possibly emerge as an area of cracking.

However on an earlier experiment when I made the size with too much water, some of the fibres within the aggregate board actually swelled up (like little viens) disturbing the smooth surface. The size is meant to insulate the board/panel from the effects of moisture, but certainly I could anticipate the different rates and reactions of the various wood fibres in the board could result over the long term with an uneven surface developing underneath the painting.