Bill, thanks for the more detailed report. The 'banging' you describe is some cause for concern. It is possible that the print head is colliding with the side walls of the printer -- not supposed to happen. Another user has reported (in another forum) that this happened to him, and he called Epson Support, held his phone close to his printer while it was making the banging sound so that the Epson service rep could hear it, and the service rep said that was bad and to exchange it.
The sound really shouldn't change as you change the Platen Gap. Does this happen with all papers you've tried so far? (or have you only tried one type of paper?)
This is what I've found last night. With the Platen gap set to normal, the printer makes a distinct banging or knocking noise, (if you made a fist and hit your desk from say 3 inches softly) and you can feel the vibrations if you put your hand on the printer.
If I then set the PG to its widest setting there is little if any noise, maybe a very light clicking sound at most. Also, at this wide setting I'm not seeing any head strikes, but at the normal setting the last 1.5 inches of the print has lines (banding / head strikes?) This noise varies with the Platen Gap setting ( I didn't even try the narrow setting)
In regards to paper, I've only used the following.
Premium Glossy Photo Paper, 90%
Premium Luster Photo Paper, 5%
Enhanced Matte Paper, 5%
One thing I must say, aside from the area of the head strikes / banding, the prints look great.
Do you have a link to the report from the other forum?
I'll be giving Epson a call after work, I'll report back what they have to say.