They're extremely easy to spot, just look on the IFoA website, which holds papers back to 1999. There haven't been any big ones recently. Also look through past SP7 exams (including ST7, ST3, 303, etc) as the principles needed for SP7 are pretty much the same as those needed for SA3, and there have been tricky SP7 ones in the past too. If you want papers prior to 1999, you'll need to contact the IFoA library - that opens up Subject G, QG, 9A and 9B.