Alejandro -

1) As the form is maximized and the PreviewContainer shape along with it (this is done by the framework I use) it causes the aspect ratio of the report to change. How can you know the report proportions in order to increase the size without distortion?
You may find this article useful also: Techniques for an alternative Report Preview which includes the sentence, "[An exercise for the student would be to] adjust the aspect ratio of the Shape to match the dimensions of the report, using the ReportListener's .GetPageWidth() and .GetPageHeight() methods".

Did I understand correctly the behavior, and is this a reasonable strategy?

I think so.

- Colin