Diving with stages vs deco cylinders is different. I do not recommend diving deco cylinders on top. You need to confirm the cylinder and gas you are breathing and cannot do that if the deco cylinder is on top. I will only run a stage cylinder on top if it contains the same gas mix as what I have in my sidemount cylinders. I also set up my regs so the 2nd stages are different enough so that I know which cylinder I am breathing from by looking at it or feeling it.
When I dive deco cylinders in open water I carry them below and use additional bungees to hold them up tight against me. They pull up in tight in the space between my torso and my sidemount cylinder quite nicely. I've done a giant stride about 6-7' from the platform to the water carrying a set of LP108s, 2 AL40 deco cylinders, and a Silent Submersion Magnus scooter without any issues. I prefer that over having anything handed down.
For stage cylinders, I do carry them on top. When I was trying to figure out how to carry them I had seen some youtube videos of other divers doing the top carry. I played around with this and initially tried to connect the top clip over my shoulder but didn't have the flexibility to do this. After talking to some other sidemount divers and experimenting I started pulling the clip under my arm and that worked much better. The issue with this was the bottom of the cylinder tended to ride high. Playing around with the position of the bottom clip I was able to find a position that kept the bottom fairly close to my body. There's no set distance from the bottom of the cylinder to position it. I ended up placing it 18 inches from the bottom but some people need it a little closer. The determining factor is how tall you are and how far apart the bottom and top attachment points are. With top mounting it's much easier to clip on in the water. While clipping on before getting in the water is possible it is difficult and the bungees on the stage cylinder attachments also make it less desirable.
When I dive deco cylinders in open water I carry them below and use additional bungees to hold them up tight against me. They pull up in tight in the space between my torso and my sidemount cylinder quite nicely. I've done a giant stride about 6-7' from the platform to the water carrying a set of LP108s, 2 AL40 deco cylinders, and a Silent Submersion Magnus scooter without any issues. I prefer that over having anything handed down.
For stage cylinders, I do carry them on top. When I was trying to figure out how to carry them I had seen some youtube videos of other divers doing the top carry. I played around with this and initially tried to connect the top clip over my shoulder but didn't have the flexibility to do this. After talking to some other sidemount divers and experimenting I started pulling the clip under my arm and that worked much better. The issue with this was the bottom of the cylinder tended to ride high. Playing around with the position of the bottom clip I was able to find a position that kept the bottom fairly close to my body. There's no set distance from the bottom of the cylinder to position it. I ended up placing it 18 inches from the bottom but some people need it a little closer. The determining factor is how tall you are and how far apart the bottom and top attachment points are. With top mounting it's much easier to clip on in the water. While clipping on before getting in the water is possible it is difficult and the bungees on the stage cylinder attachments also make it less desirable.