Yes it is cold natured but not to bad, just have baby it at first.
When we started out my son was 80 pounds soaking wet, plus a little short, I dropped the triple clamps as far as I could and set the sag then backed off the compression & rebound. (adjusting rebound helps the most as they hop around quite a bit on the stock setting)
I soon raised the triple clamps back up a little because it made the front end too twitchy.
If that does not work then you can always take the suspension into a good suspension shop and have them revalve or change the spring rates. On Race Tech internet site you can put in his weight and what type of riding and it will give you suggested spring rates.
My son now weighs about 100 and the stock suspension is still doing fine, just adjust the sag every now and then.