Agree on all counts. But what you might want to consider when it actually comes time to spray that undercoating is to deviate a bit from the haphazard application of the factory and concentrate on all of the edges of the splash shields and where they meet their mating parts. Also, that piece of closed cell foam at the bottom just screams "water trap", so coating it thoroughly in the undercoating might not be a bad thing.
If you intend for your car to be a permanent demonstration of exactly how a car was built by L.A. assembly and not driven, then reproducing the haphazrd spray pattern is the way to go, but if you want to drive your car and expose it to the weather while it's out on the road some care with the undercoating material might keep all of your hard work from deteriorating that much sooner.