Hi ho. Like I said a couple of days ago, we have templates in bluperint now. These are wireframe guidelines that show the maximum size an object can be as well as outlining some key spots in the object where it will interact with The Sims. The next release will offer this feature (as well as a bunch of bug fixes and other new features) and should be out this weekend. Below is a project I started for a new bookcase using the bookcase template. The template shows the maximum size for a bookcase and the shelf that the Sims will reach for when grabbing a book to read. No more flipping around in the Sprite Editor to get things lined up. Just follow the template and everything will line up perfectly. Enjoy.
Also just a quick support comment. Please do not install blueprint into The Sims directory. Doing so might make things unstable for both The Sims and blueprint. Why? Because both programs scan a set of subdirectories for object files. blueprint sometimes makes temporary files that are invalid and while they do get cleaned up, there may be a case where they do not. To be on the safe side, blueprint should not be installed in the same directory as The Sims.