You can cut a few coils off of your stock springs and get a spring that's stiffer! Here's the formula: new [cut length] = [original length] X [original spring rate divided by desired spring rate] X = 470mm x [.37kg/.40kg] ; X = 470mm x .925; X =435 mm After cutting [ I use an air grinder] heat the end coil back about 1/3 turn and bend it down against the next coil to get a flat end. You Do lose a bit of length but It doesn't seem to be a problem. You can at least try out the new weight before you "spring" for an aftermarket set.