I have a movie in vegas pro that is 1140x1080 widescreen HD. I want to make an avi. When I render, it looks alright, except the images where I manipulate dimensions, such as masking out something or resizing a frame. In those cases, the images are too big and expand beyond the letterbox frame. I've messed with all the parameters in the avi rendering options page, but I still can't get everything to look right. What am I missing?

And if I can get equal quality with another format, that'd be fine too.