It is actually a really easy setting to change in your configuration. Just change the Default Jog Speed in your .ini file or even easier, the setting menu or Gmoccapy allows you to change it and that will be the speed at startup.
That, however, will not change in any way the "max" speed as you referenced. It will always allow you to move the speed slider to your max jog rate or if using a keyboard, holding shift and the direction will give you max jog speed.
You can also change the scale of your turtle jog inside the settings of Gmoccapy if you wanted to make that scale at a different rate.
