Mike,
I wear a backpack, which carries my extra rod, plus extra gear. I should be more specific; the pack is an EMS top load type. Two clips secure the top, and there is a pouch in the front as well as the top. I either carry my spinning or baitcaster (both 8 1/2 feet) or an extra fly rod. Always! I fit the spare rod into the pack and secure it between the two clips. This holds the rod securely, but also allows me to postion it to the left so I can still cast normal.
As I do not yet own a boat, this keeps me very mobile. I like to fish Waquoit for the speedsters, and the hike there is about 1+ mile. I have been out on the flats with one rod, have broken that rod, and with no spare, my fishing was done. I always carry two rods.
Good Luck,
Ray G.