Ospark.com's quote section took a gerber .zip file (generated by Eagle version 3.5) and said it couldn't find the board outline. It showed a few other problems too which have been fixed, thanks to several people showing working gerber code. Oshpark's need for a different form of board outline seems to be the only remaining difficulty. I'm hoping someone who has used Oshpark (or 4pcb.com?) will send a Gerber .zip file that has been accepted to me at email@example.com. This will provide a "known good" example of a board outline that I can use as a model when generating gerber files. Also, it needn't be generated by Eagle but just be in accordance with Oshpark/4pcb's expectations.