good to go with the stiffer rates we don't have much travel to work with and the husaberg front wheel loading in rocking chassis movements like hard braking is very high.
stock travel on my bike was lucky to be 285mm actual available travel. now up to 300 and can go to 308 with a new BV.
jap forks spec 315mm travel and some measure around 320 actual used.
for sand MX with 285mm travel and 75Kg rider I beleive 0.54s would not be too stiff.