Getat(not TD) is selling a full case set for USD 35 + shipping that comes with a see through caseback. To open the caseback go to ebay and get yourself a sticky ball, never fail for me to open a pam caseback.
Still i don't think it is wise to do so as Pam with close caseback is one of the plus point to make it one of the best rep OOTB, to change the close caseback to open is just like modding your well made rep to become canal street standard IMO, no offence intended.