I tried the whole process again and this time it seems to have worked as planned. Not sure what I did differently, but the ETAs now make more sense. Now to go for a ride and see how close the hill climbs and descents correspond to the real thing!
Just started using this great website to create courses for my Edge 520. I created a course and used the timer feature, adjusted the flat speed to 19mph, and then downloaded it as a TCX file, limited to 200 course points, 300 feet before a turn, and the virtual partner shows the speed I selected. I download that file to my PC and then put it on my Edge. The turn by turn prompts appear at the bottom of the map screen right on time! The next screen on the Edge shows a cue sheet with upcoming course points and arrows showing the direction of the turn. It also shows estimated time of arrival at those points. That is the problem. Those times seem calculated on about 3.10mph, not the setting I put in the timer on plot a route. I can't find any way to correct this. The virtual partner setting on my Edge is turned off but is set at 15mph. I'm not sure that this would make any difference anyway.