I actually do not agree with the "6x is more correct than 5x". I have discussed the numbers in a hop growers forum and it turns out that 4.63 should be the most accurate number, so 5x would be better.
The math is:
1000gm as picked (80% Moisture)
0.2(1000) = 200gm is the weight of hops with all moisture removed. (20% is hops, 80% is moisture)
200 + 0.08(200) = 216 gm is the weight of hops with 8% moisture.
So 1000/216 = 4.63 is the ratio of as picked to dried by weight.
All the math above is based on the supposition that you are harvesting hops at the right timing, not soaked with rain etc.
If you have different numbers please let me know, I'm very curious
Cheers from Italy!