Boil kettle sizing questions

[sirgiovanni]

I use a 15 gallon Mega but you need to be very careful when you first start your boil. For one, that is when your volume is the highest but also, this is when you are dissolving the oxygen out of the wort. This means foamy boil over. My solution is to watch closely during the initial boil at low boil temps. Once the oxygen is out, I start ramping up the heat to a vigerous boil. Beer in your bloodstream should be the only variable to cause you failure with this procedure.

[msjulian]

If you get a chance sometime could you measure the ID of the kettle? Northern said that the measurements on their site are "approximate". I am looking at my brew structure and trying to decide if I need to make a few changes if I switch up to a different kettle.