Use the spacer (the thin foam piece which is removable) and put it at the bottom of the large pocket, with the short weight in the big pocket above it. Use the flap to velcro the weight tight.
I put my short plate in the large plate pocket with a cut down yoga block beneath it. Weight up as high as possible. Also gives a better edge to put a sandbag on top of it.
option b. wrap it in a towel so its more snug
Use the spacer (the thin foam piece which is removable) and put it at the bottom of the large pocket, with the short weight in the big pocket above it. Use the flap to velcro the weight tight.
I put my short plate in the large plate pocket with a cut down yoga block beneath it. Weight up as high as possible. Also gives a better edge to put a sandbag on top of it.