It is posible! To achieve this do the following:
After:
// sets border radius of the rail
railBorderRadius : '7px'
Add comma after '7px' and:
// Use a fixed height for the scroll bar
useFixedHeight : true,
// the fixed height of the scroll bar
fixedHeight : 50
Replace:
barHeight = Math.max((me.outerHeight() / me[0].scrollHeight) * me.outerHeight(), minBarHeight);
With:
if( o.useFixedHeight )
barHeight = o.fixedHeight;
else
barHeight = Math.max((me.outerHeight() / me[0].scrollHeight) * me.outerHeight(), minBarHeight);