May I suggest looking among the specifications, available to download via the "specs" menu item, and get three documents, in pdf format, the GM1, the GM2 and the GM recommendations specs.
These tell you what the recommended values are for various controllers, e.g. channel volume 100, expression 127, and pan centred, etc. The normal default for program change is recommended as both bank selects set to 0 and program change 0.