I converted the HPD spring rates to the EPI style so they can be better compared. Loads are Kg at 2.5 and 1.25 inches. There is also a 5% manufacturing tolerance. Let me know if I screwed up the conversion, I think it's OK though.

EPI
Green DRS16 65.8 kg 118.0 kg
Orange DRS15 56.8 kg 118.0 kg
Purple DRS17 54.5 kg 82.6 kg
Yellow DRS14 43.1 kg 65.8 kg
White DRS18 34 kg 70.37 kg
Orange DRS13 34.0 kg 61.2 kg
Red DRS12 15.9 kg 56.7 kg
Pink DRS20 0 kg 73 kg
Brite G DRS19 10 kg 55 kg

HPD (using EPI type measurements)
Plain 14.5 100.7
Brown 30.1 96.4
oarange 31.3 88.0
yellow 21.8 82.2
green 20.8 66.8

Sources
http://www.erlandsonperformance.com/...Code=primspkaw
http://www.hpd-inc.com/Specs.html