Different rates between the intermediate and heavy duty coils but heavy 75mm will be the same rate as heavy 50mm. I'll see if I can find free height. I don't know what it is off the top of my head.
I'm starting to think its a conspiracy, I haven't seen anyone yet provide the numbers on the 50mm coils and I've even tagged the design guru and the US distributor. Not even so much as an acknowledgment from them.