If you have too much credit, your score goes down. If your credit is too small, your score goes down. If you pay off your debts, if you take on new ones, your score goes up, or down. Depending on the whims of the secretive bloody system of credit scores, no matter what you do, you have little control on the bloody score.
I am a cosigner on a less than $10,000 USD loan, and thanks to it I just lost 7 points.
finances rants