Inspired by the posts i decided to make my own extension because i also think the standard pink NP foil is very fast but also very unstable. I made 3 attempts. First one out of aluminium but i think the aluminium is not strong enough for the bolts and i think they will not hold in the end. The second and third one i made out of a bar of stainless steel. I made one of 20 cm and it worked well. The only thing was that after sailing for an hour the bolts became a bit loose and a bit of slack of the extension was the result. The third one is 15 cm and very close fit so no adapting possible anymore but also no slack at all. I gave the backwing quite a bit of lift bacause i also think the standard foil has to be sailed with a lot of backfoot pressure.
You do not need any specific skills to make it and it is low cost. (around 30 euro)
i tested the extensions last friday in wind of 15 to 18 knots and made my first run over 50 km/h with it so it really works 
For the pix i added a link and i will try to post the pics here.
