Those are great reviews John.
I've had a couple of nights with the 20mm Lunt HDC and this eyepiece so far is VG. In the 15" f4.8 I notice no astigmatism at all and will try it at f3.8 once that scope is up and running. The Lunt is very sharp on the moon @ 91x, and it does exhibit a bit of off axis "gold fringing" to my eyes, not to be confused with the blue ring of fire at the field stop. The 21E also exhibits off axis fringing, thinner than the Lunt with green on one side of the moon and purple on the other. The 21E has a similar blue ring of fire.
With the SQM-L between 19.8 and 20.5 and the moon subsiding I caught the Veil and more importantly a bit of Pickerings Wisp with the 20mm Lunt/Lumicon OIII. This is a good sign IMHO. I detect a small amount of FC in both the 21E and Lunt 20mm HDC, but could be scope related.
So far I really like this eyepiece.