Tanks for the insite into sidemounts.
I have been playing with these for a while and for much of the same reason. Crawling around on the rocks in Tobermory Ontario made me realize that if I went for a tumble I would not be getting up without some help and probably back, leg, head, hand, etc. injury.
I have built a stainless steel back plate, 11gauge that weighs in a just over 14 # to that I added 2 long loops to the bottom of the plate that, when sitting upright raise it about 4 inches. I have opened the tank strap loops as far apart as possible to still be able to thread them into a dive rite venture 28# wing and to triangulate my back mount tank to fasten and stablize.
I use a bare nst dry suit for extreme cold and a white fusion for not so cold, both seem to do well. I have attached a 13# argon bottle to the back plate on the left side so that when the kit goes on (no tanks or maybe one on my back) I can hook into the suit for my inflation. This removes one hose from the twin side mounts. Or if I have a tank on my back I can additionally rig that to the wing and be ready to dive with air and use the side mounts as depth supply.
The ss loops on the bottom of my plate are 1/4 inch round and hold the plate up when vertical. They hold the lower big clips on the bottom of the tanks and are very easy to find. The tops of the side tanks hook up to the 'D' rings on my shoulder straps at chest level. I have also placed 'D' rings at my shoulders so I can adjust my trim by hooking to the shoulder rings and the tank slides up the plate loops. As you know when you do this in the water the weight and movement of the tanks is childs play. I am only using Al 80's for this learning experience with a swing of -6 to +2 of bouyancy. My 130's are another story.
Without a tank on the back the wing is held in place with an Al plate sized to fit into the centre of the wing. I did not use the wing at all on the last dive but my suit to adjust and even to trim. That is another story.
One last thing and this is where I may need some help or constructive/distructive critique. I have a hard time doing an over the shoulder shut down. I have tried every configuration from twin manifolds to 'H' valves and slob nobs. The slob nob works on the 'H' valve but I will need 3 for the manifold and that will be a management nighmare. Using the side mount rig I have mounted the back tank upside down. Remember the loops? They allow me to support the backplate and mount the tank (upsidedown) with the first stage and hoses not being used as a rest. The loops hold the whole kit up. Shut downs are easy and this tank can be used for my wing. Using this configuration the back tank holds the wing, is straped to the back plate and my Al sandwich plate is taken off.
I am using a dive rite XL harness and have woven it into the plate similar to a Holgarian. I have been perfecting it through the use of both 3 and 2 tanks (Al at this point). I am now rerigging the sidemount tanks with straps and cams to be able to add a few # of weight to the bottom of the sidemount tanks.
The maximum pressue diff between the sidemounts has been 500# and I have not seen any reason to go shorter. There is no yaw.
To summerize I have up to 200% redundant air supply, can shut down any primary easily, with a lift bag I have 200% redundant lift, My trim is adjustable in 3 steps, and my walk or jump into the water is very quick so much so that my buds with the steel 108 twins on their backs are becoming inquisitive.
Cheers.
