Chuck, you asked
Do any of you do this with the non operating engine actually feathered?
During initial training for a MEPL rating we feather an engine (usually only once) so that the stude gets to go through the full feather/unfeather drills but this is done at/above 3000ft and within easy reach of an airfield.
The course is 6 hrs min of which 3.5 hrs min is asymmetric, during this period all failures are simulated (except as above). My practise is to either pull mixture (at/above 3000ft), sneakily cut off fuel (in the cruise, at/above 3000ft) or by hiding the throttles and closing one (below 3000ft) - as soon as drills are correctly performed I set zero thrust (net effect equal to a feathered prop, typically around 10" MAP).
Asymmetric approaches are always flown with the inop engine set to zero thrust so that the engine is available if required. The only exception to this is simulating a failure below Ach when a throttle is closed once the stude has committed, it's more important to reach the runway than try to mess around with feathering drills so the engine/prop are windmilling but power is available if required.
whatunion: slightly melodramatic old chap.
As I'm sure you know there is no problem at all controlling "these kites" with an engine feathered providing the minimum control speed is maintained - whether or not the height you can maintain is sufficient, or whether you can
gain height, is another matter and depends on a variety of factors.
HFD