Wow it is interesting how people get so fixed on their beliefs based on marketing data. I doubt there is any practical advantage to the different end cap designs other than aesthetics. Lets see some real life fuel saving data for RV trailers-- wind tunnel data on semi trailers doesn't cut it for me. However, I suppose the RV manufacturers parrot this stuff in their marketing, just like they do for "built for full timing", "slam hatches", "easy lube", "wind tunnel tested rear caps" and etc.
Lets not confuse physics and practical life with markting--