I've always stuck to doing small "ornamental" retaining walls and not going over usually 30" in height. I've always thought that at the 3' and higher the wall needs to be held by geo-grid. I'm bidding a wall at this moment that is mainly an ornamental wall with not much soil to hold back, but the highest point of it will be roughly 40" tall for 6' then step down to about 30" for another 12'. I'm using Versa-lok mosaic stone and was wondering if I would need to put one pull of geo grid into the wall? Maybe 3-4' into the backfill? Let me know what you think.