started trimming back the sides.

Doing this by looking where the windscreen touches the top skin and prevents it from laying in a relaxed way along the sides.
The sides of the windscreen will still have the tendency to stand wide at this point.
When you press the sides inwards towards where they need to be, you'll see where the windscreen touches the top skin and prevents it from going down.

That's the spot you need to trim back further.