In a word, no. Redesigning the rig is going to be far less advantageous than keeping the rigging
fresh and the rig tuned.
Your boat was designed in 1967. It was probably built prior to 1975? It would certainly be a good time to consider replacing the chainplates should they still be original. It might also be a good time to consider replacing the standing rigging
as well, depending on how long it's been standing. Such maintenance
will go a lot further to keep your boat happy than adding double lower shrouds.