Hmmm sounds strange that. If you can see the bearing tool then it should just work. Its just a static overlay (using the Alpha Channel) like a picture if you will, where all but the bearing tool is transparent. So it should not change the scale.
What resolution do you run there...might have something to do with it, but don't think so.
To upload a picture you should use a "image hosting site" like
http://Filefront.com or
http://photobucket.com/ make a account and start upload your stuff, then use the url link under your image given by the hosting site and paste that in your post. Check by using "Preview Post" if it shows OK.