Can I use a bit of coarse sand under a 2' high planter wall w/ pillars? I have the trench pretty well leveled with 6" of compacted RCA but when I test a few blocks of the first row I see some spots need a bit of tweaking. (perhaps 3/16" or 1/4"). Does the wall block & pillars need to go directly on the RCA base or can I screed a bit of sand under it? I'm doing a patio as well and realize that a 1" bed of sand is needed under the pavers, but I'm thinking perhaps only about half that under the wall would really help me get it perfect. Yes or No?