on the top toolbar go to 'window' scroll down to 'document window size' make sure 'constrain window aspect' is unchecked and put in 400 width 500 height (or any number set with the same ratio)... now check 'constrain window aspect' & 'OK'... then go to your 'render options'... check 'New Window' fill in the 2400X3000 size & render. it should work fine (I just tried it & it worked for me :-)