yeah, birail, I've also gotten birail 1 to work mostly - i think the reason why it usually fail is that the ends aren't intersecting the rail curves or that the rail curves have a different number of knots... or if the curve is over 90 degrees - apparently it don't like that neither. Hm. I had birail 2 work once as well with really exciting results - it got me to believe that birail 3+ must be a most amazing too capable of creating long, complicated, ever evolving organic mechanical shapes at the drop of a hat. haven't got it to work yet though. Oh and one thing i didn't catch at first was that you choose a profile curve and then have to press enter and then you get the prompt to choose rail 1, then enter and then rail 2... or perhaps it's only me who was so blind as to not get that right off...

Have you seen the NURBS modeling tutorial with the suburu? Incredibly helpful if very long and convoluted. Server seems to be down at the moment but it was fine earlier. Link is:

https://www.blissdd.com/

to get the tutorial you will have to register. Worth it though.

The model looks great! More!