Chuck,
That is a good point and something I had not considered.
Wouter,
I have both teleconverters, the tc17 and the tc20.
I don't think the new zooms are an option for me because I am using an F4s and an F100.
Craig,
Since I am shooting film I don't think I could work with the slow max aperture of the mirror lens.
Thanks everyone for your responses.