I spoke with John at Ledcorp about this, and I guess it's pretty much okay...
I mean, of course using the 4-cell bulb in a maglite would be better, but isn't the bulb in the maglite directly in contact with plastic and NOT the aluminum anyway???
Since the 3 and 4 cell pro bulbs have resistors in them, it's also okay to run them with a bit more power, although you should make sure they're heat sinked somewhat...
Craig, do you think the probulb shouldn't be used in plastic flashlights? I mean, the manufacuter recommends maglites, but I don't think these bulbs were made for aluminum flashlights only. They are being underdriven, so I would think it's okay to use it in any flashlight, as long as you're not overdriving them too much...