Well what I have done is removed the dead pedal, drilled it and bolted the plate on.If you look at it-shine a torch in the footwell-there's a biggish screw in the centre at the back roughly behind the brake pedal,you need remove with a large straight driver and a smaller allen key type plug affair on side of the dead pedal itself,take these out and it slides up and off. Drill it and bolt the plate on then just fit it back.Its dead easy!
Yes,self tappers were going to be plan "B" if I had to dismantle half my car to get the dead pedal off,but it really is very easy to remove and refit so I figured drilling and bolting is a better method. It is a German car afterall!