mercy you got that thing into the 500's!!!! ive never come close to getting it that hot and it looks like you were using briquets (sp) did you do anything special to get it that hot? those drums look really good!!!
Believe it or not, the initial temp was above 575 deg F for a couple of minutes (see pic below, my probe pegs out at 575). Granted, the probe was placed on the grate at the hot spot in my PBC (my hot spot tends to be near the wall opposite of the bottom vent hole).
So I've noticed a lot of folks use a half basket or 3/4 basket of coals, etc. I've found if I want a rip-roaring hot cooker for stuff like chicken or to get a good char on a steak, I don't skimp on the coals. I was using the trusty Kingsford Blue charcoal, basket filled generously to the top (I'd say heaping rather than level). Also, for hot cooks, I'll let my coals go for a bit longer than the initial 20 minutes, making sure the entire basket is ashed over and glowing.
I've yet to experiment with other types of charcoal (e.g. lump or Kingsford competition, both of which burn hotter than KB). That's my next adventure!