@Baycode : thank you, that was Way Above And Beyond The Call Of Duty . Senn double flanges will get ordered ASAP.
I went into a search mode for tips as shallow as possible - and found on DX/Tinydeal/Focalprice/ETC this tip is rather common:
It appears to be 2-3 mm after being mounted, with bore approx 5 mm.
The bore on new WSH could be enlarged - by carefully triming it with say a drill bit of 7-8 mm diameter - so that it would retain present diameter at the side facing the driver, with conical shape and larger diameter facing the ear - or drilling trough the entire thickness with the drill bit of approx 6 mm to produce the constant 6 mm bore. Drill carefully by hand - any motor drilling would overheat/tear/destroy the delicate tip.
Yet with any so shallow tip, an inscription with invisible ink that turns visible just prior to inserion into the ear , is required. Reading :
Clean the earwax first before using !