Hi Paul. Getting the required number of images at high res will take some time, and using your dob you will inevitably end up with a fair bit of field rotation. Lack of tracking may also impact on your image quality at very high res (ie you're shooting at a moving target).
I have an alt/az mount & find this problem, even though I've never tackled anything as ambitious as what you're proposing. I have stitched up to 15 moon images together to create mosaics though (I use a NexImage webcam BTW). Photomerge in PS is good and you can rotate individual images to match up.
I've just started using another stitching program, Serif PanoramaPlus1, which I got free on a CD 'giveaway' with the May "Sky at Night", a British astro mag. It's an older version (hence the giveaway!), but it has some amazing features including being able to bend and otherwise manipulate component images. The latest version apparently has heaps more features. Link to web site is:
http://www.serif.com/panoramaplus/panoramaplus3/
Good luck with your project!
Cheers -