I am afraid you may have to go with a sub report unless you can shrink what is in the rectangle because the rectangle must be large enough to hold what is in it. For instance, I can put two tables inside a rectangle and then colapse the hight of the tables to almost nothing and then colapse the rectangle to that size, then if I do not hide the rectangle, the tables and rectangle will grow to show what is in them, beyond what the tables or rectangle were sized at, but if I hide the rectangle, it only takes up that miniscule size. Your example looks complex so I am not sure what you have in that rectangle and if you can work with this idea but I think that is the only way to get it to work.
HTH
Chris