Thanks, Jim, that's what I was looking for!
One minor detail - as mentioned, I create multiple plots, using the "By" attribute. So I had to loop over all obj elements:
n = N Items( obj );
For(i = 1, i <= n, i++,
Report( obj[i] )[AxisBox( 1 )] << Min( -75000 ) << Max( 75000 ) << Inc( 25000 );
Report( obj[i] )[AxisBox( 2 )] << Min( -75000 ) << Max( 75000 ) << Inc( 25000 );
);
This works, but please let me know in case there is a more elegant way.