Hey Keith,
I thought you fell off the face of the earth.
Revolutions suck. They crack around the hub and shouldn't be used. Panasports are not the lightest wheel out there, but seem durable for GT cars on slicks. Circles in aluminum are light but flex a bit (might not be as much of a problem with radials, compared to soft racing slicks). Check with Circle about their availability. I was looking for some 15s last month and they said they were out of aluminum 15" rims, and due to a switch in manufacturing, they wouldn't be able to produce them for 6-8 weeks.
For the bucks-up types, Kodiak and Jongbloed make very light real race wheels, but they can cost the price of a cheap IT car.
I think 15s would be the way to go for an IT Z car. More clearance for brake ducts, small unsprung weight penalty, easier to correct roll center.