Don't know how a Designer Feedback forum would be right for this question...
To change the performance of the 172, as you may know, requires modifying the aircraft.cfg and possibly the .air file. I suggest looking in the FSX SDK, if you have FSX Deluxe or acceleration. Air files, however, are much more challenging to edit. Making changes to the cfg should be enough, though.
Editing the panel, well, that is harder to explain. You can change/move gauges with FS Panel Studio. It's not free, but very useful. If you can, you can edit the panel.cfg in notepad, which can take a long time to get things right.
Hope this helps!
Brandon 8-)