You should include which floorplan you have, as well as your present A/C unit's model and size, in order to get better information to your question.
My experience with Majestic line has been limited to Cruise America rentals, and on larger 28A model (about 30-ft long) the A/C was marginal at best when parked in sun during day, and that's mostly in May. I can only imagine that in July or August it could get a little warm in the south.
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