Skeeter,
You make some valuable comments and I too employ similar techniques when flying my very under-powered Rotorway Exec.
Regarding the option of maintaining IAS however, it can cause some confusion to inexperienced pilots who do not consider that the ASI under-reads significantly when the wind is not 'blowing' down the pitot from dead ahead. This gives the helicopter a significantly higher groundspeed than desired for such an approach. This inturn gives our inexperienced pilot a harder task at the bottom than it would if the groundspeed was carefully controlled from the top of drop.
Notwithstanding any of this, my original post was aimed at Raven2 whom I beleive to be less experienced due to the nature of his question. Furthermore, based on his 'name', Raven2, I'd assumed he was flying an R44 Raven 2 and therefore tailored my answer to fit the aircraft type he'd be flying.
Cheers,
J