We recently converted part of the garage into a bedroom w/bath with a total area of 355 square feet. They installed a Mr. Slim Mitsubishi mini split with a rated capacity of 12000 btu/h and a minimum capacity of 6000 btu/h. SEER is 13.5 btu/h. When it is very warm outside and the unit is running it is always very humid inside, even when the "dry" mode is on. The humidity remains between 55 and 65 percent. Is it because the unit is too big? The a/c guys said they don't make a smaller unit so they installed this. Actually, they need to replace it anyways because they inadvertently installed a unit without a heater. Should I ask for a different type/size unit? Any other ideas?