Saturday practice is just that...practice. You do not win anything. Basically it is 4 heats. 2 of which you will actually drive, and 2 of which you will be responsible for "working" the course. On a decent Saturday you can get about 18 practice runs in. Far superior to the 3 you get on a trophy day. Also, the practice course is damn close to what the actual curse will be on Sunday, so you have a huge advantage. If you cannot go both days, shoot for Saturday.