Hi Paul. As you know, I've picked up your thread on Facebook but will reply here as well in case anyone else has the problem.
John Paul from Poole in Dorset has proved to be a reliable source for used Eriba awnings, towing covers and winter covers so that's why I asked if you were an Eribafolk Facebook member.
As I explained on there, the door position on the two most popular versions of the Troll, are as follows.
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The 530 door starts approx 1020 mm from the front corner seam of the cover
The 540 door starts approx 640 mm from the front corner seam of the cover and is in the same position as all of the Familia and Triton range.
See diagrams.
530.jpg - Bild entfernt (keine Rechte)540.jpg - Bild entfernt (keine Rechte)
Randa