Never, ever, ever, use Parcel Post to ship a frameset, or a complete bike, for that matter, in my opinion. Unless you want the frame damaged!

Stay under 108" - I've shipped up to 62 cm. c-t frames by Priority Mail in the past. Waterford's box supplier makes a great box. Waterford calls it their 'export box.' I bought some of those at one point in the past, and they worked great. They were not expensive, especially considering how strong they were.