The previous style had two thinner pieces of webbing for vertical mounting, so you could put a belt slide in between to keep it from sliding. I never figured out why they changed it. I usually use a belt slide (tri-glide) to keep the weight pockets from sliding around and it works OK, but hard to get it snug enough so there's no wiggle in the weight pocket. I dive a TransPac harness here, but it should be pretty much the same as the Basic continuous webbing (which I have for my tropical setup with the travel weight pockets). I push the weight pockets as close as possible to the backplate
For horizontal mounting, the weight pockets have a little tab on the bottom that slides into the 2" webbing, and you can put a tri-glide up against that to keep it from moving. Personally, I like the vertical orientation because it takes up less space on my waist strap and when I'm diving, it puts the weight pockets horizontal instead of facing down (I think that's why they changed the design a few years ago to add the velcro in addition to the plastic snaps)
In case you didn't realize it, there is a left and right side weight pocket, the right hand pocket has the Dive Rite logo patch, the left side is plain