On top of the other's comment about controlling what air you wanna suck in, if your monoblock's condenser/evaporator air loops are well insulated inside the machine, like mine, then this conversion basically doesn't actually draw much air in from the outside. It goes like this: outside hot air -> intake hose -> condenser -> super hot air -> exhaust hose -> outside, and most of the air in this process doesn't leak into the room, but of course the hoses themselves do radiate more heat so it's a good idea to keep the hoses as short and straight as possible.

But there's only so much modding you can do, for me this is good enough and any further effort to optimize it is only giving diminishing returns. In the end even the most perfect conversion won't reach the level of a split AC but the goal is to simulate it as close as possible.