I want to buy a fountain pen that I can use for shaded script calligraphy when it's not convenient to use dip pens. For example, an old Waterman 12 or 52 with fine or extra fine flex nib. But I'll consider any brand or age of pen so long as it writes fine but opens up well (>1mm), is at least 4.75" long with the cap removed, and is in good working condition.

This need has been met. I'd delete the post now if I knew how.