I suspect the F3 is quicker Block 1 & 2, but probably not 3 (unsure about that one). I once had a race with a German F4 low level over the sea whilst on TLP. He had me initially, but I overtook as we got....err....quite quick. As the F3 is faster than the GR1 (as it was then), I guess it's faster than the F4. Not that it matters.