Well, looks like the end of the burning season might be here for me. I've been keeping the 503 active, mainly because I didn't want to have to restart if it got cold again, but with this Saturday expected to be 80*, it's probably time to pack it in and clean it out. I'll probably load the remainder of the bag I opened yesterday and call it good.
I've been running the 503 with the restrictor at 1/3 open and the damper at 1/8 open most days, turning the blowers on at night. On colder nights I'd open the restrictor to 1/2 open and the dampers to 1/4 open to take the chill off. Still, I've been averaging about 20 lbs. a day. But this looks like my last bag. I still have the better part of a ton left over. I'll try to post my total coal use when I get a chance to figure it out accurately.
Needless to say, this thread has been a great resource for all 503 owners out there (although it wasn't intended as such when I posted my installation photos). Let's keep it going next season!