This is a project revisited...as they often are after realizing your first answer was a horrific failure.Our first attempt at curtains was created with the primary goal of being able to remove them when not needed so that E's interior remained clean and modern (and to avoid drilling/screwing into the bus).  We sewed rare earth magnets into the corners of black fabric to hold the curtains up, and the effect was near blackout conditions inside the bus with complete privacy (tested and proven effective while stealth camping in parking lots last summer en route to portland.).
The problem was, that as soon as we removed the curtains they became a bundled mess of fabric and magnets that stuck to the side of the bus and took a scientist to dissect and reassemble into curtains.  Several pinched fingers later...we decided to start over with a primary goal of function and a close secondary goal with form...  We borrowed another sewing machine from one of Jen's coworkers and went back to work...

While we have never been fond of the hanging curtain look (at home or in campers), we decided to use curtain cord to allow easy opening/closing of the curtains and simply had to find a way to install the cord without screwing into the bus unless absolutely necessary.  We went back to our good friends at Lee Valley Tools and their magical rare earth magnets, but this time only where we didn't have to risk injury in removal. Seriously, if you have used these magnets before i can tell you...while they aren't cheap, they are frighteningly strong and we recommend them highly...just watch your fingers when snapping them together.  The magnetic cord holders worked perfectly to attach the ends of the cord, and provide enough strength to still pull adequate tension on the cord.  We ran the cord the entire length on each side, and used another cord holder in the middle with the cord running straight through the hole for a nice clean connection.The curtains look great and Jen is working on sewing ties with small magnets to hold the curtains back when open.  These also work great to hold the bottom of the curtains against the bus for maximum privacy when closed.  Best things about the new setup is that if we know we arent camping for a while and want to remove the curtains all we have to do is unhook the cord or simply yank the magnets to remove the entire setup!