In no way am I a helicopter designer, but looking at the jet efflux thrust line, I assume it was necessary to raise the rotor to get the rotor forward thrust line in balance with the jet efflux.
If you kept the current R44 head height the jet efflux looks as though it would cause a pitch up moment which would require too much forward collective to make a viable machine.
This may be complete b***t so I seek the expert advice of the pprune design team out there.