Thanks for the very helpful information in my previous thread. I scanned a sample showing the light leak I described and was wondering if you could help me diagnose it. I did get a couple of good exposures from the same lens, which leads me to believe it may be a sporadic problem with the shutter not closing all the way. I tested the lens on 2 lensboards and it sits flush and light-tight so I'm pretty sure the leak is not between the lens and board or between the board and camera. The previous owner told me the lens was sitting idle for over 2 years so it's possible a CLA is in order.
Here's what it looks like: