well you have to experiment with that but one can do another thing... get a hood, get an exhast fan fitted and then get the vents fitted on it... in this way,, it will also be protected from the rain. if you can find some solution that engine remains cooler, the ac will definetely work better in mehran and for that purpose you have find some option to throw all the heat from the engine compartment to the outside and let the fresh air enter from the from grill.
Well i have heard this is the only solution for mehran when everything fails and it even works in the city where there is a lot of traffic and car gets more heated due to frequent starts and stops.
So its upon you if you wanna try it or not. I cant give you a guarantee but i have only seen a couple of cars like this and have heard it works.