On Monday, May 4, 2015 at 1:41:36 AM UTC-4, mike wrote:
On 5/3/2015 8:44 PM, CarolG wrote:
replying to scott21230, CarolG wrote:

Hi. My main concern was that I did not want to put nail holes in my vinyl
windows. Instead I used 4 pieces of wood: 1) I used a 2 x 4 that fits
at the bottom and in front of the vinyl
window, and the air conditioner rests on this board. The length is the
exact measurement of the entire ledge so that the 2 x 4 is wedged tightly
on both sides and cannot come loose. You can make it very tight with
shims. 2) I have one board that sits on the outside of the vinyl window
in the
track from one side to the other as tightly as possible. The air
conditioner sits on this on the outside of the window. (mine was 1x2x28)
It is important that your air conditioner has a bar that you screw into
the top of the air conditioner. This will hold the air conditioner in the
window when the window is closed behind the outside of this bar.
Now it is time to put your air conditioner into the window as directed, so
that it is resting on the 2 x 4 on the inside and the 1 x 2 on the
outside. As you bring the window closed behind the metal bar it will
overlap the bar by a good 1/2" holding the sir conditioner in place.
3) I put two more pieces of wood between the top of the window casement
and the top of the window. (mine were 1 x 2 x 13 each.) This keeps the
window from opening and letting go of the air conditioner (make sure they
fit very tightly).
My air conditioner had L brackets, 1 for each side of the air conditioner
and I screwed these to the 2 x 4.

Hard to visualize your situation.
I'd suggest that you install the air conditioner so that there is no,
zero, none, not any,
force applied to ANY of the plastic window parts.

the original question goes back to 2006.......

one of our vinyl windows warped and had to be replaced because of the weight of the very lage window AC unit that cooled our entire main floor