One drop won't hurt. And you probably need not add to both exhaust ports, for they both lead to one unit.
I also have an earnest recommendation. If you have not already done so, take a camera of some kind and open up the hull of your Leopard, taking photos as you go step by step. I recall years ago opening the first tank I bought. I was doggone concerned that I might ruin it. I proceeded carefully because at the time there was nothing online to show me what I was getting into. But each step of the way I learned about how the whole thing works, building my confidence, too. I have never regretted that first move, for it started me on the most interesting aspect of the hobby and gave me the ability to fix the inevitable minor problems.
Here are three YouTube videos showing how to open various HengLong tanks. None is exactly the same as the Leopard we both have, but all the HengLong (and Taigen/Torro, or Coolbank, or TongDe) tanks are similarly constructed, to once you have the general idea, go for it!
https://www.youtube.com/watch?v=x6qG_paXYeI
https://www.youtube.com/watch?v=lW29I4Aenl8
https://www.youtube.com/watch?v=zweB6Bgl990