Hmmm, a small trampoline, cat ladder perhaps? Actually 250mm isnâ€™t that much. I reckon a cat could be trained to jump that. (You could then have endless fun bolting the flap shut every now and then and watching a concussed tiddles stagger around the kitchen)
Ok, sorry. The panel is just the easiest place to make the hole. Provided the door isnâ€™t too thick for the cat flap I canâ€™t see any reason why you couldnâ€™t fit it in the middle of the wood below the panel.
If your cat doesn't appear to want to jump you could always attach some rungs to your door on both sides to give him or her something to climb up. If your cat is anything like mine it'll love anything ladderish!