I came to gardenweb originally to ask a similar question. I think that you have already answered your own question. Since 1128's and the others were both listed, you already know that Troybuilt believed that whatever those numbers represent in Quality is up to their standards. However, from experimentation, and the 'block' already being extended, you already know that the 9245's are probably too big. The only question left is if the 1128's have stretched a lot or only a little. If only a little, then you must need one inch shorter belts. Otherwise, new 1128's are probably right. So, you go to the parts store with your old belt and see if 28" belts are shorter or a lot shorter than yours.