The hard aftermarket foot pegs are slightly lower than the original rubber pegs, so I was never really happy with the brake lever position after I installed the new foot pegs.
The brake lever position is not adjustable on the F800 because the lever just hits a fixed stop (that is also the brake light switch) when you release it.
But I managed to move the brake lever position anyway by fixing a small stainless steel block to the brake lever with 10 second glue and a zip-tie.
Only thing left was to adjust the clearance at the pushrod on the master cylinder.