A 30 amp mini fuse is the correct size..Contrary to what your dealer says..A breaker should not be used, only a fuse. The reason being, a fuse will blow in an instant, a breaker will not, which can cause damage to the gearbox for the landing gear legs. If you are blowing fuses it is because you are not watching the legs as they move upward or downward. You MUST turn the switch off before they they reach the end of the travel. It would be nice if Heartland or Lippert would install a micro switch to shut them off before they do this but that hasn't happened yet. There is no reason to run the legs all the way up. You can leave them extended an inch or two. DonThe same thing has happened to me (extending or retracting the legs to yhe limit). The Dealer gave 30 amp breaker that pluged int0 the inline fuse holder. So far no problems. I think I will use a marker to mark the legs as discussed.
Dennis1948