Oil level/Crankcase capacity/Oil Dipstick

Hi I'm a proud owner of a 2005 Malibu Maxx. When I change my oil and filter and replace the oil it only requires (4.5) quarts to reach the full mark on the oil dipstick, even after the car is driven many miles (3000) between changes. This was true even when the car was under warranty but the dealer thought that the technician over filled the crankcase, however, now that I change my own oil/filter and add the oil one quart at a time I find that to add the recommended (5) quarts would show approx. (.5) quart over the full mark.
My questions:
*Have you come across this situation with other 2005 Malibu (3.5) liter V6's?
*Could the oil dipstick be missing some part that allows it to penetrate the crankcase further than it should? (in its present form it has (1) 'O' ring (0.07MMX6.07MM) on the yellow handle)
*Am I correct that the crankcase capacity is (5) quarts when the filter is changed?
When I drain the oil I allow sufficient time to completely drain. This is a low mileage car (approx. 11,000) miles and I have had (0) problems and am very satisfied with it in all respects. It leaks no oil what so ever and I neither want to over fill it or under fill it. Any help/advice you can give on this subject will be appreciated. Thanks