Congratulations !!
On my camera the L-fn is assigned to recall focus - to be used with M-Set where I set the focus point.
The L-fn2 button is assigned to switch instantly to BIF settings by - Recall shooting function (without the hold) . It has a submenu which I have set up for :
Frame Rate (Release mode) - 20 FPS
Shutter Speed 1/2000
Aperture - lowest possible - in this case 6.3
ISO - auto
Metering - Centre weighted
Focus Mode - Auto Area
Subject detection - Bird
This is my normal setting when I am not shooting birds in flight
8 FPS
1/250
F8
ISO fixed
Matrix Metering
Focus mode - Wide Area C1
Subject detection - Bird
If i press the L-fn2 button it switches to BIF mode. Release the button and it is back to regular perched birds mode.
In addition, if in case I want to stay on BIF settings for a while - without having to keep the button pressed - I have the same settings assigned to my DISP button. That would be a click on - click off operation
I find the ability to switch instantly between BIF and perched bird mode is one of the most useful things in modern cameras and I aim to exploit that fully.
Enjoy the new lens.