Perfect timing..I have been trying to figure out how to do the hip/shoulder mount..does anyone have a photo of the set up by chance?
Right now I run twin independent steel 72's but am thinking on running my twin alum 80's instead, and packing the steel 72 as a pony. Yeah, probably overkill, but would like to get in the habit of it for when I pursue the technical aspect of the sport.
I assume you are talking about how to rig the stage bottle itself.
This is how it is done
hogarthian style.
The Hog rig uses normal hardware store items. Dive Rite sells a it that substitutes nylon webbing for rope, but they both accomlish exactly the same thing in the same way -the hardware store route is a lot cheaper and easier to find, the DIR version is a little cleaner looking.
The key elements are to have the upper clip tight to the bottle right at the base of the shoulder of the tank where it begins to bend in toward the neck and to leave a few inches of tail for the lower clip so that the tank can move with some freedom to streamline most efficiently.
With regard to the BP/wing's harness, you need the D ring on the shoulder strap just slightly higher than the upper part of your arm pit - high enough to keep the stage in tight, but low enough that you can reach the D-ring with either hand. The left waist D-ring on the waist strap should be in the center of your hip, half way between front and back.
I would advise against using a steel 72 as a pony, AL 40's and Luxfer AL 80's have very good bouyancy traits for stage use, they are slightly negative when full to about neutral when 2/3rds empty with the reg attached and very slightly positive when completely empty. In other words they don't create major trim issues at any one point in the dive. A steel 72 on the other hand starts off 6-7 lbs negative when full with the reg attached and never makes it to even neutral bouyancy when empty. This leaves you listing slightly to port with a full tank and, since you need to be weighted so as to drop the tank if needed, you have to weight yourself so that you can drop the tank late in the dive and still be neutral at a 10' safety/deco stop. So in effect, it creates both trim and over weighting issues compared to an AL 80.
Most steel tanks (not all as some are too negative for some warm water situations)make very good back gas tanks as they are non-ditchable so the negative bouyancy of the tank at the end fo the dive can be used in place of lead weight you would otherwise require with twin AL 80's on your back which would otherwise be positively bouyant when near empty.
