My wife and I finally got our used custom Bushnell. The fit is as good as I had hoped for; we should be able to dial it in perfectly after fixing the stem lengths.
I was wondering if there was anybody out there who would be willing to loan or rent a telescoping stoker stem so that we can find the right length for my wife. The current 18cm is too short. Once we figure out what will work best, we can ship it back and buy an appropriate length stem for keeps.
Oh, and here's a link to my blog post about our bike.
I've adjusted the cranks per tandemgeek's advice (thanks again), so that I am not forcing my wife to do more work.