That is correct the flap will sit on top as all the catchers do now. You will have to cut a section in the lower left hand corner of the catcher to allow the catcher sides to come up against the rear of the mower. Lift the catcher up as high as it will come and mark on the door where you need to fit a piece of angle on the underside . Rivet/weld it on and it should be fine. You can also put a piece of angle on each side of the flap, this will prevent the catcher moving sideways and help stop any clippings flying out
