Generally, software that needs to be signed is in sis format. If the software in SIXX format can't be installed, just sign it.

First, you need to download the DOSPY signature tool and key file from Saipan Forum.

Put the certificate, DOSPY signing tool and certificate signing key in the same directory of the computer, double-click DOSPY signing tool to run the program, right-click the key, "Import Key (S60 Phase 3)", and right-click the certificate, "Import Certificate (Replacement)". Right-click the software you want to sign, "Sign this file" or "Sign all files" ... The signed files are all in sisx format.