too my knowledge there was only 1 spring rate for the delta88 F41 spring package (cause it wasn;t supposed to be offered with the auto air leveling ... nor did it come s/c ... for my year anyways...
infact most ppl are amazed that my car even had the f41 available... even on Hbody specific forums
anyways... as for catching air... I doubt it as far as I can tell I'm the most aggressive driver this cars ever had and I haven't come close to launching it airborne

I don't doubt that it's sagged a little but even then it's still got well over 3inchs of fenderwell gap
it won't be till late winter early spring that I will be looking at ordering a set of springs... and since DP is the only company to date I can find selling aftermarket springs I'll probably have to end up custom ordering a set
but what your saying is... If I can get the serial # for my spring set... you can make a set of 2inch lowering springs to the same spring rate?... can I request a little more spring rate and progessive coils?
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86 delta88 stock for now
http://www.cardomain.com/memberpage/667152
Mods starting in October and throught the winter/spring... to... however long it takes