testuser: if one types /Volumes/swap/gimp (on my system, at least) into the gimp's preferences panel under directories (in the bottom blank, not the top) *does* change the gimp's swap file to that location.
BSDimwit: thank you for clarifying the disk changing operation under BSD CLI. I do understand that my two partitions are seen as parts of the same filesystem by Darwin; all I needed to put this into action, as well as the gimp issue, was the syntax, which you were so kind to provide.
Everyone: I am a longtime Photoshop user; nonetheless, I can't recommend the gimp strongly enough; of course Photoshop is without peer (nothing else is even close, if you ask me), and Photoshop Elements provides a welcome solution for not-so-serious (or well-heeled) users, but the gimp has more than a useful feature or three, plus it's free to *X users. Particularly if you habitually work in XDarwin (or KDE, Gnome, etc...), the gimp makes a perfect tool. Install it today!