Hi Michael,
thanks for your explanations. I missunderstood the manual. There is an illustration that made me think that you can work with multiple rails. But now i see, that's are 2 Rails and 1 Scale Curve. I'll try it with a network. And i'll first build a clean version.
Greetings, Wolfgang

I believe that you can consider in your particular object's case the "Scaling Rail" as a third rail!

Ps You have also the middle section overlapped! ;)

else Network works like a charm : Yo have just to close the extremities by a plane if wanted!

Hi Pilou,
is the solution shown by you the network-solution?

Yes ;) was writed "else Network works like a charm"
but i have killed first all overlapped curves! (middle section, side edge...)