Is it possible to buy a 7 day base ticket and use two of those days to go to different parks, rather than buy a park hopper? So I will only need 5 days, but a couple days I may want to park hop. For example, can I use day 1 ticket to go to MK in the morning, then another day's ticket to go to epcot in the evening? This will be cheaper than buying park hopper, but not sure if it is allowed.