Best by far are Japanese Reggae dealers, Dub Vendor. Use their own custom made boxes that are about 2" thick & packed with cladding and still tape up the records with cardboard stiffeners.
Strangest I ever had was a cheap record I won from the states & it was just stuck between 2 other records. One of the records used as a packer was Etta James - Seven Day Fool. Mint, unplayed & never even took out of the sleeve. Result.