1966 Barracuda Restoration Project

I have a question for anyone that has ever used raptor liner as an undercoating. When taping around the engine bay area along the sub frame, where do most people tape to separate the frame rails from the engine compartment. Seems like the frame rails go right into the engine bay and I don't want to see bed liner when I look into the engine bay. I guess my question in a few words are: where do you draw the line? Thanks FABO!