I just tried test booking a specified cabin, Calif Coastal, and can do so. Mid aft , mid level, balcony for 957 vs 928 pp for chosing vs let Princess do it ie guaranteed. Stopped before actual booking to avoid tying up a cabin for this test. This is usual the guaranteed is the lowest for a specific catagory but you can be anyway within the catagory, I rather pay a little more and get what i want.