Many of the WC snakes I've seen are quick to ball up and will continue to exibit that behavior even after several years in captivity. Of course these WC were in breeding collections and did not get handled on a regular basis like a pet would. I've never owned a WC, so I'm not sure if they would abandon the 'ball up' behavior with regular handling.
I don't think I've ever owned one that would ball up after they reached 300 grams or so. I'm not sure if that's due to them reaching a certain size, or if by the time they got that big they'd been around long enough to know I wasn't going to eat them.