Klammer,
I will be instructing with GVC.
Did you get accepted? School sold out super quick 2 months ago. It was amazing how quickly it filled up. Got the second to last instructor slot.
Pointers? Since its your first time there, learn the line and get consistent. To be fast at the Glen takes a leap of faith as it can be beautifully intimidating. The most important turns for quick laps there are T1, the esses, T10 (esp. T10. A fast run through that one will be very, very intimidating) and T11 (almost anti climatic after t10).
Leo,
For most events so far this year I ran a square stock wheel set up using 18x9,5s all around with no spacers. Used street tires and stock wheels to let my wife learn the car and track after a 5 year hiatus. With the stock wheels the gap between caliper and wheel is about 3mm.
Last week finally put her on BFG R1's on 18x10 Apex ARC8's. Huge room between calipers and wheels there.