Hi, depends very much on your weight and the fork rate, standard is, I think, 38kg....far too soft and get a lot of fork flex, when cornering or going thru ruts the fork brace helps. The best option is off-course get a company doing springs just for your weight. I tried about everything to get the suspension right on the 400r, ordered Eibach spring at 47 kg spring rate, better but still too soft, then I ordered the fork brace, an improvement for sure, but still I was unhappy, then I cam across Cannon Racecraft and I enquired springs for my weight, I was paying 300 dollars for that upgrade but I don't regret it a bit, the fork and shock work in harmony now and I don't get any fork flexing at all. Spring rate front 64kg and 13.8 kg on the rear. But at the end it is always the choice of the rider:
1. What terrain you're riding
2. the riders weight
3. riding level
4. set the rider's sag (if you cannot make it work, then you need different springs)
For my very personal choice, I like a more motocross-like suspension, I have now my suspension about 95% where I want to have it. I am mainly riding single track Enduro here in Chiang Mai. The XR400R is a great bike but the suspension really sucks. Cheers