The support arm isn't structural. It's a mechanism to hold the window open on the ground/low speed, and stop the window opening all the way at higher speed.
Check the manual for the a/c. You'll find most Cessna singles specify the max window opening speed to be Vne (possibly Vno for the very fast types eg C210. Can't remember).
As I mentioned before, the most awkward part is making sure you don't detach the end of support arm that connects to the spring. A real b@stard to attach again because the spring disappears into the window's frame. The design must have been outsourced to B@stard's Inc.