A good rule of thumb when doubling the boil volume is to cut the bittering add by 1/3rd. In that recipe, you could move half of the bittering Cascade add to 15 minutes.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk