I didn't see anywhere whether the broiler should be on low or high? Should I simply try both?
Also, Scott - what do you mean when you say a lot of folks have ovens that require the use of higher oil and sugar concentrations? Are their stones simply not coming to temperature? Or maybe the oven heat setting does not go past 500? I have a pretty cheap oven and I'm not having any problems, so I'm curious.
Marie, my broiler doesn't have a low setting. It might be worth trying to see if you can get more even browning with low.
It'll be nice to have some IR thermometer readings to confirm this, but I believe that your oven runs a little hotter than most, which is allowing you to hit 6 minute pies with your stone, and possibly even 5 minutes. Many people have ovens that have a 500 max dial temp, but, at the same time, many 500 deg. dial temp ovens will actually go much higher- as high as 575. Most of the 550 dial folks go to about 575 as well. You have a small percentage that will exceed 600, but I think the bulk is 575. At 575, only certain hearth materials, such as 1/2" steel plate, give you 4 and 5 minute bakes. The stone you're working with now, at 575, won't break 7 minutes- which is why I'm practically positive that you're exceeding 600.
For your average person working with 7+ minute bakes, you're not going to see much oven spring without an extra dose of oil.