Not
@wreighven, but I did a little look into this and may have addressed in this old thread:
Model X Travel Trailer Consumption Analysis
That said, it matters most if the 3" rise increases the frontal area outside of the slipstream of the X. Most likely it does, since the airflow hugs the X pretty closely. Since the Basecamp X is 7' wide, it adds about an additional ~252 square inches of frontal area to the A in this formula:
View attachment 712765
Which means it has a linear proportional relationship to the drag force - whatever percentage of frontal area increase that represents, that's the percentage of drag force that you'll experience.
My Airstream 22' Sport is very low. It bottoms out regularly if I'm not extremely careful, and still bottoms out occasionally when I am extremely careful. I have resisted the lift kit on mine for this reason, though with my longer range X, I might be willing to take the hit now.