Personally I wouldn't bother with undercoating. Pretty much all old cars I've kept, I've got undercoating done. Why? Because they are Karachi cars and I am OCD about any noise coming inside due to tiny holes in body. So I take it to body shop, jack it up, get the rusted parts fixed and then undercoated. Undercoating also serves as a way to compensate for eroding of Teflon coating in old cars.
New cars have no such problem that's why I don't get my new cars undercoated, including my Turbo. As @arkhitekt has said, Civic X undercarriage is well shielded, so there's hardly any reason for undercoating.