Zeiss Jena Pentacon 6 lenses, DOF button

I have two CZJ lenses both with DOF preview levers. On one, a Flektagon 50, the DOF lever actually is reversed and allows to be used as a "pre-set" lever. On the other, a Biometar 80 the lever functions as a normal DOF preview. Comparing the levers they sit in opposite directions based on a small notch on the lever itself and, of course the spring tension is reversed. Both are post Zebra, MC models. The way I use both these lenses with adapters I quite like the Flektagon set up as a 'pre-set' lever and am wondering if this is something someone did before I got the lens and also wondering if it might be easy to convert the Biometar to do the same. Does this ring a bell with anyone? The end result on the Flektagon as it is now is that one can set the aperture, then depress the lever with a finger to open the iris and focus, then release the lever for shooting. Eventually I will go inside and see if I can sort it out but it sure would be nice to know if this is a regular modification. If I am in a wrong forum or someone knows of a better place I'd appreciate the direction.