There are so many really nice old 16 gauge doubles out there, why bother with 12s and especially 20s. I do have one lightweight (6,17 lbs), long-barreled (75 cm) very well balanced 12X65 hammer double that I use for hunting sometimes (got my last geese with it, this past December). I feed it the same 28 gram 1200 or 1300 fps hunting loads as I do my 16s. Only thing different I notice with that 12X65 is that it is not nearly so svelt or so easy to carry all day long as the 16s.
Overall, my 16X65 and 16X67 hammer doubles have taken at least 90% of birds I bagged in recent years -- ducks, geese, desert quail and bandtails. In desert quail country in Arizona one can buy 16 gauge 28 gram loads in all sporting goods stores I have visited and even some gas stations.
Who would bother with that misanthropic, one-barreled rattletrap gun that Remington made?
Niklas