At the club where I tow our procedure, after the glider releases, is to take 15 seconds to go from full climb at 65-70 kts, typically, to the descent airspeed of about 110 kts whilst maintaining more or less constant RPM (not constant speed props) and then a further 15 seconds to reduce to 2300 which gives about 1000' a minute rate of descent. At about 500' the tug is levelled off, without moving the throttle, allowing the speed to reduce into the white flap band and the rpm will of course drop further. Power is gently reduced on final. Since this procedure has been in place the number of cracked cylinders has become negligible - before it was not.