Safe to open window sash with installed AC (with brackets)?

I have an LG LW1804ER window air conditioner that was professionally installed in an apartment building window. It does have support brackets outside that angle from the bottom-back of the unit and rest against the brick facade of the building. I'm on the fifth floor, by the way.
I need to open the window sash to do a couple of things. I'm going to put a "Stop-Drop" foam covering on top of the external AC enclosure to dampen the sound of the upstairs neighbor's AC unit, which is directly above mine. It drips water constantly, which is like the proverbial water torture inside our apartment. As an aside, this is what I'm going to install:
http://stop-drop.com /
Anyway, I also want to clean the windows, which are vinyl types that swing into the inside of the apartment for cleaning.
My question is this: There are just a couple of small screws fastening the top inside bracket of the AC unit to the sash. I can't imagine that the window itself is supporting too much weight of the AC (in other words, the natural force of the AC to want to just fall out of the window) because of the brackets underneath the unit. But, I'm not sure.
I don't want to remove the screws and open the sash only to have this thing lurch toward the outside and somehow fall. Yeah, yeah, with the brackets, that shouldn't be possible. But the only dumb questions are those that aren't asked. Should this be safe for me to do? It will only be me working on this thing for the time the window(s) will need to be opened. I'm no weakling, but I only have two hands, and can't do the work I would need to do with only one hand, lol.
So, am I good to go on this project? Tks.
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Are the AC brackets bolted to the building? If not, then I wouldn't think that you'd want to do anything with the unit unless there's someway to support it from the inside.
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They're not bolted to the building, but wouldn't any outward/downward pressure on the unit (by removing support from the window sash) just increase the pressure on the support brackets against the building? In other words, essentially making the support bracket holding power even greater?
Aimless in Charlotte wrote:

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Can you pull the unit out of the casing?
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Moe Jones
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Funny you mentioned that, because I just stopped at a hardware store for the "Stop Drop" foam covering I mentioned above, and that was one of the suggestions. I wouldn't want to pull it all the way out as it's pretty heavy. It would be a bear for me to get it back in without damaging some radiator fins and whatnot. But maybe slide it out far enough so it still has some window support (sill) and still allow me to do my work.
Moe Jones wrote:

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If I were you set up a small platform, like a small table, and have a friend or two help you slide out the window unit and put it on a table then complete your work.
Do not forget to unplug the power cord from the outlet before removing the window unit.
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Just wanted to close out this thread with how I dealt with this. I did end up just pulling out the unit enough so its weight was balanced on the sill and not in the enclosure. At that point, I was able to install the foam top (which works great, by the way!), and also clean the windows, which sorely needed them!
Thanks for the replies.
Moe Jones wrote:

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