[funkychips]

Fiddleheads are very sensitive to pressure and temperature fluctuations. When I've first gotten my repotted capensis the new leaf stems plus fiddleheads turned black in two days, only to be replaced by new ones a week after. It all depends on the environment you're keeping it in. I don't have a regia but like Khoas mentioned you'd probably want to keep it cooler first to minimise the stress it got during mailing and see how it goes. Hope that helps.