Interesting. Works Performance does this with their shocks, they stack one spring on top of another. I'm not sure about the math, but the 2 springs are softer than either spring by itself. When the smaller spring fully compresses the larger spring takes over with it's higher rate, so you get a dual rate suspension, similar to a progressive spring but with a defined line where the rate changes. WP uses spacers to allow you to preload the small spring to adjust the rate change over point. By not using a spacer your friends Version 2 rate change came later in the stroke than your Version 1.
2009 Wee Strom ABS (current)
1987 Harley Low Rider Sport (current - with 205K miles)
2009 Aprilia Mana 850, 2006 SV650, 1984 Yamaha Virago 1000 (all sold)
Silver Strom Club Member #11
Wee Farkles: Russell Day Long Seat, Madstad with Moose Adventure Shield +4'', SWMotech Centerstand, 1'' up & back bar risers, Givi XS308 Tankbag, Aprilia mirrors, Framesliders, Fenda Extenda, Elka Shock.