Put 8" of mixed 50% clay cat litter and 50% 1/8" Mexican stone into the 33" tall ROS-4 posts. This amount dampened vibrations most noticeably in the bass but the highs did become slightly cleaner.
Added another 4" to the posts, the highs became cleaner and the bass snapper. So far so good!!!!
Tomorrow I'll add another 4" and hear what I get!