Thanks, I ended up achieving this by coding the HCB via Mobiflight:
-4096 (>K PROP_PITCH1_SET) and -4096 (>K PROP_PITCH2_SET)
... and make sure you delete any other feather bindings in MSFS you may have previously had.
Once I pass either prop. lever through detent it selects full feather on that prop., but I assume there is not a graduation possibility in any case. I have checked the movement and each prop. RPM operates independently into feather as above.
I have a question though, if I leave the prop levers at full fine, and shut the engines down, the blades appear to be in full feather when they stop (despite not moving the prop . levers at all) ... is this correct?