I don't have a toy hauler but: I do have a 31' TT that had one A/C unit from the factory. I live in SW GA. and the heat/humidity is brutal at times. I added the second A/C unit where the vent was over the front bed, ran 10 ga. wires through plastic "wire mold", used a heat gun to heat the plastic wire mold as the ceiling is rounded toward the front, then ran the wires through a cabinet, down the wardrobe then into the front storage area. I installed a 6x6 electrical box to make up the wires and added a 20 amp push button marine grade circuit breaker. The wires go through the sidewall of the TT to a weather resistant male connector. As "Retired SJO" stated I also use a dedicated 10 ga. heavy duty extension cord to run power to this A/C. I use the 50 amp service on the power pedestal with an adapter for my 30 amp TT and use the 30 amp service at the power pedestal with an adapter for my 20 amp A/C run. Never have had a problem and the TT stays so much cooler.
2015 FR Freedom Express 310BHDS pushing a 2014 GMC Sierra CC