I would appreciate some suggestions for stitching together scanned
sections of large format diagrams (schematics); photo editors such
as Photoshop or the GIMP require a lot of resources, are often
sluggish (if you don't have very fast hardware) and require a lot
of tedious manipulation to achieve the result. There are photographic
panorama stitching tools but these too may have problems with a large
number of high-resolution scan sections on slower hardware. Microsoft
Photo Editor 3.0 had features that made the task quite simple, but
it is difficult to install as a stand-alone app without a version
of Office.

What are folks using for a simple solution to this task (other than
purchasing an expensive large-format scanner)?

Michael