The Hyperco springs arrived today. The first ones I received turned out to be old stock, and Hyperco offered to exchange them for the latest designs.
I weighed all the springs, and Hyperco has apparently been making continual improvements. These are all 10" 2.5" ID 525#.
#1 2.42 kg (9 coils)
#2 2.15 kg (8 coils)
#3 2.11 kg (7.5 coils)
#4 2.08 kg (7.5 coils)
For reference, the Swift 10" 65 mm 504# weighs 1.92 kg. That's as rated, I haven't weighed it, but Swift's ratings have been right on.
The 560# 9" 60 mm Swifts I bought earlier -- I was going to use them until I re-measured and found I couldn't get the height I wanted with them -- weigh only 1.57 kg.
What matters much more than weight, is stroke. The Hypercoils I have now look like they have 5.75" of stroke before coil bind, maybe more. It's pretty cool to see these spring designs improving. The 504# Swift spring is rated to have a max stroke of 6.1".