When you do not use a STA with the Mach V, there is no offset. None. The cylinder sits on the spine webbing on the wing itself. That is 0".
I measure tank offset from the back plate. Anything between the tank and the plate will offset the tank from the plate. 0.0" offset would be possible only if the tank was in direct contact with the plate.
Typical wing construction, using "spine webbing" and metal grommets will result in a minimum offset equal to the height of the grommet. This is typically about ~1/4" Any fasteners used to secure the wing to the plate via these grommets will add to this value. Most divers want some means to secure or locate the wing on the plate, in most cases this means bolts of some type through the wing grommets and back plate.
I took a pair of calipers and it is .36, not .55.
I see you now agree that the typical low profile STA offsets the tank by almost twice the figure you first claimed, .36" vs "less than 3/16"
In the case of a grommeted wing and STA the total offset can be as much as the .36" you note for the STA + the ~.240 for the metal grommet, totaling ~.6" That actually exceeds the value I stated. (.60" > .55")
DSS singles wings do not use metal grommets. We use custom molded elastomeric "windows"
These windows, installed, are about .120" thick.
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DSS uses a compressible elastomeric Locator to position the wing on the Back Plate. These locators have a "head" on the tank side of the wing that is about 0.080" thick in the free state.
I have seen photos of your rubber locator and it sure is not .15 on the majority of diver's tanks.
With a DSS singles wing all that separates the tank from the plate from the tank is the thickness of the molded "window" and the head of the rubber locator. .120" + 0.08" is about 0.2", in the free state. Unlike metal grommets and metal bolts, these elastomeric components compress when the cambands are closed, reducing this 0.200" offset to about .15" as I have previously stated. The center portion of the DSS elastomeric "wobble stopper" is of a similar thickness.
Tobin