makton3g,
Don't ever lay the saddle bags against the body panels unprotected because you'll have scuff marks on the paint in less than 2 miles. Dirt will get between the bags and bodywork and act like sandpaper ruining your paint in no time flat!
I don't use soft luggage anymore but when I did I'd use clear plastic box tape like this
http://www.officedepot.com/ddSKU.do?level=SK&id=172056
laid down in strips long enough to protect the areas where the luggage touched the body panels. I'd put down 4 or 5 layers which would last over the course of a weekend trip. Afterward I'd peal it off and use spray wax to clean off the tape residue.
If you plan to leave the bags on all the time just keep an eye on the tape for wear but change it regularly (every couple weeks) or it will be too hard to remove and the tape glue will be a lot harder to get off once the tape is removed. Worked for me...
dc