Frank,
There are various ways to set the break point on our engines. Load on the motor (as Brett suggested) is one way, here I would try a prop with either some undercamber (the RMS props have 0.020", or just sand some in at the tips) or one with thicker or wider blades (BTW, Zinger props come with the flat leading edge). Another option is to open up the venturi size say one #drill size at a time, this reduces the suction and can increase the point at which the engine will switch. As you do this you could get tad bit more power and burn more fuel.
You didn't indicate if muffler pressure is being used, if so, he could try running open uniflow venting (make sure the vent line is to the inside and pointing into the free air stream about 1/4" off the fuse side. You may need to combine a couple of these (i.e. open vent and bigger venturi) to get the break you want.
Another option is to change the run style from the 4-2-4 break to a high rpm/low pitch. In this setup the prop is pitch down to 4 or below and the rpm is brought up to a solid rich 2 cycle. On many ships is pretty close to constant speed as the low pitch allows the ship to drive through the maneuver with minimal lose of speed and hold back when being pushed by the wind.
In either case you may need to adjust the line length to get the lap time you are confortable with after you get the engine run you like.
Best, DennisT