Waren9
Yes I have and 1Nm/10HPa works well in practise.
Go Soaring
For 320Kts descent try 2 x Height + 10% + QNH Corr + Wind Corr + Decel, for the portion of the descent that will be flown at 320Kts. Use 3 x Height for the portion of descent below 250kts.
E.G. FL400; 2x40= 80 + 10% = 88NM.