I, too, happily use the SG20L for 16 ga RGL loads with 3/4 and 7/8 oz shot bars.  Actual payloads are less.  I tried about every 20 ga wad before coming around to the SG20L.  Orange Dusters work just OK, occasional bloopers.  I don't think I've ever had a blooper with the SG20L.  It has a short shotcup, so I do get some leading.
I think you'll find there are other wads that work well in 16 ga RGLs:  the DR16 and CB 16 ga wad are two.  The former is best for lower payloads.  The CB clone wad will work with a measured 7/8 oz drop.  The RP OEM wads (R16 and SP16), of course, also work fine with higher payloads.
Sam