Just finished my exterior setup for the single-hose penguin — a few observations

I did the exact same thing with an old Delonghi Pinguino last summer. Moving the noise outside is the only way I can sleep, but I ran into that same thermal cutout issue when the afternoon sun hit the balcony. I ended up building a small plywood enclosure with plenty of vent space just to keep the sun off the white plastic. It dropped the intake temp by about 5 degrees imediately. Regarding the positive pressure, I found that instead of an extra fan, cracking the window in my back bedroom about two inches worked wonders. It creates a natural path for the air to flow thru the hallway. Without that "exhaust" point for the house, my unit was basicly fighting a wall of air, and the airflow through my 3-meter ducting felt almost non-existent.

Just keep an eye on the drainage. When I moved mine outside, the higher humidity meant the internal tank filled up every four hours. I eventually had to run a permanent vinyl drain line down to my potted plants so I wouldn't have to keep going out in the heat to empty the reservoir manually.

I tried the "exiled" setup with a 12,000 BTU Honeywell unit last August, but I struggled with the cycling. Since the thermostat sensor is located on the intake at the back of the machine, it kept reading the ambient 38°C balcony air and running the compressor at 100% til it nearly froze the coils. I eventually had to open the casing and extend the thermistor wires by about three meters so I could poke the sensor trough the window seal into the actual room.

The positive pressure you mentioned actually worked against me because it was pushing my cooled air out through the bathroom vents and under the front door. I found that cracking a window at the far end of the hallway just a tiny bit created a better flow path. Instead of using a helper fan, I switched to a thicker 150mm insulated duct to reduce the static pressure. It’s not as quiet as having it on the balcony, but it stopped the unit from short-cycling and saved me a bit on the electric bill.

You shoud realy look into the static pressure limitations of those integrated centrifugal blowers becuase most portable units are engineered to exhaust against minimal resistance, meaning your long ducting likely shifted the operating point on the fan curve to a region of significantly reduced cubic feet per minute.

While the positive pressure scenario you described technically forces air out through building envelope gaps, you are asking a low-torque motor to overcome the friction loss of that ducting while simultaneously battling the back-pressure of the dwelling's volume. I woud suggest calculating the equivalent length of your ductwork to ensure you haven't throttled the evaporator's airflow below the threshold required to prevent coil icing during high-humidity cycles.

I'm pretty new to all this DIY stuff, but how do you guys handle the rain? If I leave my unit on the balcony like that, I'd be terrified of a sudden downpour shorting everything out. Do you have to bring it inside every time the clouds look grey, or is a simple cover enough to keep it dry? Also, since it's pulling in air from outside to cool it, do you notice more dust or street smells coming into the house? I really want to try this to get rid of the noise, but I don't want to ruin the machine or make the air quality worse.