H99 like all helicopter stuff it is all to do with energy ( power )management.
Show your student it takes more energy to hover downwind ( due to us not being able to hold a steady hover ). This then moves on to losing translational lift early and at some distance and height from LZ. Therefore more energy required !
So engine can only give so much energy, so we know we are going to use more energy to hover and last bit of approach. Add to this the amount of energy ( power ) required to slow the aircraft both horizontally and vertically . So easy answer to use less energy, ( so one has more energy to play with ) is to have a shallow approach ! Try a normal approach then turn it round ( ie same heights, distance and ground speed ) student will immediately slow helicopter down and have a larger rate of decent to get down, therefore building up a lot of energy in the airframe ! Does the engine have enough energy to arrest the rate of descent, student pulls lever up , result nose goes up slowing the rate of descent, or so he thinks , but at the risk of coming off of translational lift, more energy required, which will rapidly increase ROD, thrust is now not vertical it is is behind as student is flaring the helicopter, so more energy required, now tail wants to weather cock, so more energy required, still out of ground effect so more energy required, sloppy handing as shown in hovering downwind so more energy required and so on