Hi Steve,
At least the ALPY is stable enough not to have to go to the extreme of taking flats with the scope still aimed at the target like you have to do with the LHIRES if you have a camera with small scale ripples.
http://www.astrosurf.com/buil/fringes/index.html
Before I had the calibration module, I injected the light from the RELCO calibration lamp via a reversed flip mirror. Perhaps a diffused incandescent light source could also be used this way to produce a flat.
Cheers
Robin