My solution, for what it is worth, is to bolt an aluminium strip to the existing accelerator pedal (to fit behind it) which then extends the pedal towards the brake for the amount needed. The advantage is that the ali (I think I actually used some left over carpet grip things) bends to the same shape as the existing pedal, you only need to drill a couple of small holes in the existing pedal and you do not need to bend it in a way not intended. If you need to adjust the amount of overlap you can just drill new, or extend the holes in the ali.
Mind you, I still have trouble getting it right when it really matters on the track!
Mike