What spring rate will suit my Konis?

[ts@n@k@s]

As in title, i desided to buy a pair of the bolt on coilover kit from T3
http://www.technotoytuning.com/productdetail.php?p=278

The thing i dont know is what spring rate should i choose.
I use longstroke konis in my hachi, they are in very good condition.
The car is a daily driver and occasionaly drift, so im thinking of use stiff springs, ( something like 5-6 Kgs in front)

Are konis capable working with that spring rate? Should i have the shock all the way stiff to work ok with the spring?

Does anybody uses or used konis longstroke with stiff springs? Impressions? Problems? Anything that could be helpfull...