The rim could be the source of your problems, but another possible source for holes in that area is force applied to the valve stem from a pump. Hand pumps can be prone to pulling the valve stem side-to-side if you're not careful and have been known to rip a valve stem out. I've had a floor pump with a really tight chuck that ripped out a valve stem when I tried to disconnect it. I've known of at least one person who puts a nut from a threaded presta valve on the inside of the rim so that any force on the valve stem pulls on the nut, not on the rubber tube. I suppose that might also possibly shield the tube from being pinched or punctured at the hole if that's your problem.