Installing inexpensive level indicators in the cab area so the driver can make the RV level when it should be level is very easy.
Lay a cheap circle bubble level back on the floor next to the refrigerator and jocky the RV around until this level indicates "level". Leaving the RV like this, glue two of the stick-em'-on tube bubble levels in the front -> one on the dash in front of the driver's seat indicating "level" (this will indicate side-to-side RV levelness), and another on the driver's side door indicating "level" (this will indicate front-to-back RV levelness).
Now .... whenever both of these two cab levels indicate within one-half bubble of level ... the refrigerator area of the coach is also very close to being level. We find that it also feels just right in the RV walking around whenever both cab levels indicate within one-half bubble of level.