Isn't the SOP to limit your speed to VMO-10kts below 8000' (or is it 10)? I doubt it's changed. So that'll be 235kts.
It ain't just about climb rate but just being slow. What about getting in the way above 3 or 6000'? How fast is your extensively calculated climb and cruise speed? 200 odd knots isn't it? If you actually follow the correct climb procedure you're down to about 165kts at FL250.
I have flown the Dash and I know how slow it is in reality.
P.s. It's more than just a windscreen limit. Have a look for the Q400 vs. Eagle incident where the bird smashed through the wing root and caused some pretty major problems.