ahhhh.... Brad!!! that makes so much more sense! i've been scratching my head the the last few days trying to figure out how the springs are being preloaded when the lower perch is adjusted.
altering the shock travel poses another question - does the characteristic of the shock change depending on it's rest height? i.e. would the ride quality over bumps change if i had the ss kit set to max height, and then changed it to min height? assuming of course that i don't hit the bump stops or bottom out.
according to the instructions that come with the ss kit, the oem upper strut mounts need to be reused unless i have the ss kit which includes pillowball mounts:
http://www.tein.com/tech_info/inst/km64u.pdf (last 2 pages). however tein doesn't list such a kit for any mx5 except the NC in their product lineup:
http://www.tein.com/price/mazda.html 
PASHN8, i think the general consensus is that flex isn't necessary unless you do a fair bit of track or autox work. the extra adjustability simply isn't required on the street, unless you want to lower the car dramatically without sacrificing suspension travel. the ss kit is capable of handling mild track work.
ss and flex have different height ranges, because the overall shock length can be altered on the flex. you will need to get out a tape measure to determine which kit will give you the height that you want. height ranges can be found here:
http://www.tein.com/price/mazda.html (upper figures are mm, lower are inches). stock heights figures are in the sticky on the top of this forum.
i am looking at buying from
www.949racing.com or ebay US. i want to take advantage of the australian dollar and i have enough faith in japanese products to overlook any potential warranty issues. under US$1k excluding shipping sounds like a pretty good deal.
after looking at the height figures myself, it seems that the ss kit may have the front of my NA lower than i want - the range of adjustment is 312/341 to 282/311 front/rear, so even on the highest settings the front is still 8mm lower than mazda's minimum recommended height.
i wonder if this is high enough for the front lower control arms to be parrallel to the ground at least... i'll have to get the jack out and take some measurements on the weekend.
