A perfectly acceptable and very effective technique in fixed gear singles operated from real world short strips, and is particularly important in Cessna's. As was mentioned in an earlier post bringing the flaps up significantly reduces lift and thus transfers the weight to the wheels which greatly aids braking and steering. If you don't believe me land your Cessna with flaps 40 and then immediately get on the brakes, the wheels will immediately lock up and start skidding, however if the flaps are raised very heavy braking can be used without skidding the tyres. I do not think it is unreasonable to ask the pilot to manipulate the flap switch during roll out in fixed gear aircraft. It is a different story with retractables, however. For those aircraft I teach that the flaps are not touched until the aircraft is clear of the runway.