You mentioned that you can program it into your TX, surely if that's the case for the cost of 1 Servo I can't see why you'd be considering doing it any other way.
Put the flaperons on a switch and if you don't like it or you find it's great for take off and landing but horrible for general flying - problem solved just flick the switch back !!!!!!!!
Not only that but if you're not sure how it's going to react, fly it up high as you normally do and then flick the switch and bring the speed right back and see what happens - again don't like it flick the switch !!!!!!!
Also if it's not enough, land adjust rates on your TX accordingly 20 seconds later you're taking off again !!!!!!!!!!!
Just my pennies worth but I would have thought it's a no brainer ??????