Just in case someone faced the same scenario; I figured out that the page Width can be increased as required and not limited to the A3 size, in my case the users didn't require to print the report so I increased the Page width enough to fit the 79 columns. This can be done by selecting the page and changing the Page Width…

Hi, I'm not certain what do you mean by going to Excel layout, Do you mean using BI publisher tools to create an Excel template?

A3, with landscape layout.

Thank you ! It was really helpful to discover this option, however as I don't have access to the instanceconfig file, I used a URL to point to the report and it was opened with the parameters included.