Considerate: Here's what I can come up with off the top of my head for oversleeping:
As you said, one alarm is too easy to turn off. Three is overkill. Two is just right. I strongly suggest putting both alarms out of reach of your bed and in different parts of the bedroom.
Watch what you eat when you're getting close to a nap; preferably, eat nothing at all in the hour beforehand (for me it's the two hours beforehand, but my schedule has six-hour cycles instead of four). You don't want digestion and/or blood sugar level to mess up your energy level and cause your body to sleep too soundly.
In darkness, your body produces melatonin, which makes you sleepy. For that reason, if your room is considerably darker at night than during the day, you will be more prone to oversleeping at night. For this reason I keep a lamp on at all times and my blinds closed, so that the light level in the room doesn't change too much from day to night. I'm able to sleep fine with dim or moderate light (which this setup provides), though I suspect bright light would be a little more problematic. (Once I'm better adapted I think this setup won't be as necessary.)