If you are using the latest version of AudioLabel, you can select the "Canon - All Models Tray J - Print Directly on CD" template in the "Change Label Template" dialog (which is the same as the MG7150). We will be adding the Canon MG7150 to the list of printer templates soon.
All of the Canon disc printers have a tray letter stamped on the plastic disc tray. So regardless of the Canon model number, you can select the correct Tray letter from the list of Canon templates.
Please let me know if you have any other questions.