Reporting Services :: Determine Objects Inhibiting Horizontal Shrink Of Tablix And / Or SSRS Report Size?

I am working on complex invoice document that handles various types of invoicing, credit, and progress bill customer facing documents.  I am faced with same problem I see many SSRS devs posting on.  And that is extra blank pages, being generated because the report width exceeds the width of the page.

My problem is I cannot shrink the horizontal width of the tablix and therefore the report width either...

While I would have done things differently if developing from scratch, the tablix in question has only one column and objects contained in rectangles are placed in the row/column cell.....The link to the image below shows the row I am currently working on.  Essentially all the client wants a columnar report with column lines, closed footers, etc...  so rather redoing the whole tablix, which I still might do, I am using rectangles with the column then lining them up.  Anyway, that is a whole 'nuther post.  My specific questions are:  

Invoice in Report Builder

1. In the image I have selected the parent rectangle.  The children are other rectangles and the data is with grandchildren textboxes that exist within those rectangles.  I clearly have a bit of right side white space in the main parent rectangle, but there is no sizing tool on a hover... just move tool.  And if I change the rectangle size in the prop form it just snaps back to the cell width.  How do I size the parent rectangle and keep if from expanding.

Here I am guessing that to actually reduce the horizontal width of tablix and then the report, I have to first decrease the parent width of the rectangles that occur in each row?