newly installed picture window bends under pressure
Each window manufacturer has an engineering department that can help you calculate the maximum size for your particular location. 

Each region in the U.S. has a wind load requirement. Based on that wind load, each brand of window and each series (style of window) can only support a maximum window size. 

Here’s their customer service info:

https://www.alside.com/support/contact-us/

I’d call and ask for their engineering department and be prepared to give them the overall size, style (brand series, like 1700 Series, etc.) and number of panes. They can quickly tell you the maximum size allowed in your geographical location. 

Remember, it’s important to get this right or you’ll void the warranty. BTW, if it’s oversized, I’d ask for a refund from the installer. The engineering department can email you the maximum size in order to not void the warranty that you can show the installer.