render size fix

there is 3 problem

1. if i render scene

i use render outputsize;[1600 1200] command

but render dialog window did not changed that value

2.if i render scene

i use render outputsize;[1600 1200] command

new window is made

that is some complex in my monitor

3. i would like to fix render position in my lcd monitor
but if i render scene , render window is center

is possible that fix ?