Agree with you on the need for tweaking, but you may need to look at the width of your report body along with the size of your margins - together they need to fit on the sheet of paper you are printing too.
If your list object is 11x8.5 then it is probably too wide and too tall - the body of your report should be more like 10" wide, assuming landscape layout with .5" margins on both left and right.
Nothing in your report should be wider, or you can run into odd paging problems.
Also, the height of the list object should be as short as possible, usually.
As far as tweaking goes, I have found that keeping things from touching sometimes helps - make your grid finer than the default, and leave a grid square's worth of space between objects, and between objects and borders.