You have to decide if you wish to do a long hose rig or a conventional rig?
Long hose rig - where you breath the PRIMARY second stage on the longest hose which routes under your arm and around your back on a 60 inch or 72 inch hose (sometimes a 40 routed simply under the arm) and the SECONDARY is fitted to a 22 to 26 inch hose over the shoulder and is equipped with a necklace. You donate to the OOA diver your PRIMARY and you switch to the SECONDARY. Usually both second stages are otherwise identical. This is typical rigging of many technical trained divers especially if they do overhead penetrations because the long hose affords single file escape from narrow passages.
or;
Conventional octopus rig - where you breath a PRIMARY that is routed over the shoulder on a 24 to 30 inch hose and a so called OCTOPUS is routed under the arm on a 36 to 44 inch hose (usually yellow) and is generally clipped with a break away release (though it may be necklaced with a QR knot). You donate to the OOA diver the OCTOPUS and you retain your PRIMARY. Generally both second stages are not the same (though they can be). Most common and most popular and taught to 96% plus of all divers including probably to you.
There is another set of variations;
Integrated power inflator as octopus - You breath a PRIMARY routed over the shoulder on a 24 to 30 inch hose and you donate a Air II type device to the OOA diver and there is no conventional octopus.
and;
Integrated power inflator as secondary - You breath a PRIMARY typically on a 36 to 44 inch hose routed under the arm. You donate to the OOA diver your PRIMARY and you switch to the Air II type integrated inflator. There is no conventional secondary second stage.
There can be other variations (pony/aux bottle augmented, Spare Air) or nomenclature and notice, I am not really telling you which to use. I typically use the conventional rigging along with my wife but may also use the long hose rigging. Nit a bad Wiki here:
https://en.wikipedia.org/wiki/Buddy_diving
I am not sure I understand an 18 pound wing and an aluminum tank and a stainless plate. The 18 pound wing is more typical of tropical and warm water diving with an aluminum or plastic plate and with limited exposure gear and aluminum tanks. Temperate conditions, jack of all trades, 5/4MM suits more typical a 30-35 pound wing, stainless plate and a steel tanks (generally more negative than aluminum tanks).
N
---------- Post added July 21st, 2015 at 10:07 PM ----------
These work well retaining an octopus second stage, fasten to the shoulder D ring, very common:
Trident Silicone Wrap-Through Regulator Octo Keeper Hol - Gear Clips & Lanyards : House of Scuba
N
I'm in 8/7 solafx and have 18 lb ditchable.
