Why 2 lines ?
Seems very easy :)
But maybe I don't understand the question :)
(a little image of the question can help)

Hi Pilou,
I tried that too, but noticed the end wall gets thicker with the scale.



Cheers

Aaaaaaaaaaaaaah! :)

Thanks, everyone ...

It looks like the two line cut is the best solution but it is easy to keep the original curves for the inevitable changes.
Michael, I'm glad to hear that you will be looking at this in the future. Keep up the good work.

cheers,
eric