I have owned several RV's with rubber roofs. I have never had one that had bubbles. Mine are multiple bubbles from dime size to silver dollar size. As for having a huge balloon bubble while going down the interstate, How would I know?
I see RV's like that all the time. But they are going one way while I go the other way. Outside of getting another fellow RV'er to watch for me. Which is not easily done either. I can tell you.... I am currently parked in Houston Texas where for the past 3 days we have been experiencing monsoon's 3-5 inches of rain at a time. NO LEAKS so far.