Hi and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, the G5RV in order to work several bands therefore would not be an "ideal" SWR load. And the Yaesu by design also has its limitations of what it can tune/match.
Still, should you venture to try, perhaps the discussions HERE and HERE may shed additional insight.
Of course as in most workarounds/modifications, it may or may not work for your particular equipment, void any applicable warranty and may even possibly cause a hardware issue hence 'consider only at your own risk'.