B21 said:
Angle of dangle, wind direction etc..
You're missing the temperature impact, which is commonly forgotten, but as soon as someone reminds you, you think.. "Of course!".
The angle of the dangle is inversely proportional to the heat of the meat, provided the maxis of the axis, and the gravity of the cavity, remain constant.

ldman:
I saw set of 4 roof seals go up on ebay for $80 last month and picked them up just as a backup for the future. The price was irresistible. They are in better condition than my current ones (still not leaking).