Good luck trying to find an answer on this one! They are very secretive (which is BS) about springs rates.
There was a long thread on this over in m.net, do a search.
youre right, i have to please the bnd (german pendant of the c.i.a.

) to bring me these informations
its not lifesaving 4 me to know that, but i am intersted, but in two weeks i will know, if my setup is right 4 my butt (konikit "newstyle" with progressive 54mm fcm-bumpstops and fcm-shockmounts, h&r adjustable hollow swaybars f&r and "perhaps" a butterfly-brace), i think it will be a day2night-feeling after these 110,914miles (178500km)
and it seems that i will change the suspensions at 111,111

i think than i have a good ride the next 111,111miles
nicolour-contrast with your tsi, i got a pair this weekend on the year-annual of mx-5.de for a few bucks, now im thinking about to paint, mariner-blue or black? when i see yours, i think they will be black
these 13"rotas rox - very nice tam!