I weigh 70 kg (154 lb). I got a 4.8 rear spring - it was the only way my sag settings would work out. I have been very pleased with the results. The bike feels lighter on the front, easier to pop wheelies over logs etc., and the rear is generally more compliant and breaks traction less. There seems to be very few of us who go down the "softer spring path". I also find it is a better match for the stock front springs - maybe just try the rear first? this works for me!
I believe the 200's have a 5.0 as standard.