Thanks for your help. So, in my car, there is a beam in front of the right seat.... I found nothing on it. To check the other beam underneath the seat, I have to demount the right seat, right?
Hi Klaus
My memory is apparently not what it used to be.If it ever was.

When I went for a ride on Sunday, I saw that the chassis beam on the +4 is in front of the seat.
It's a galvanized chassis, very difficult to see the no.
You can use a light to create some shadow,