I have seen PLt files with 5-7 significant figures.

It all depends on the size of the image and the software that is sending it out. Also the setting of plotter units. A small thing with a low plotter unit setting can give really bad results. Making it larger before exporting or upping the plotter units will increase the definition. I generally use the default plotter units of 1016, (I think). [Plotter units are, again I think, the steps per inch.] [Maybe the steps per plotter size, I am a bit confused on this one. I have not fiddled with the hpgl in about 20 years.]

Philadelphia, PA (Really Bensalem)

When you finally understand it completely... it changes.