I'd point out that in a typical setup the splitter is located in the actic and putting the PI up there means you need AC power. On the other hand placing it next to the receiver means that AC power is available. And the DTV splitters I've seen are marked DC In and Dish out.
I could do either setup in the RV but follow the splitter labeling. Plus at home when I leave in the RV all power is turned off at one location ie Blue Ray, TV, PI, etc - note the receiver is moved to the MH so no recording at home.