I read on Vansairforce about a RV-12 accident caused by a distracted pilot who forgot to latch the canopy prior to takeoff.
The RV-12 hit the runway while the pilot was trying to latch the canopy.
When I neglected to latch the canopy before takeoff, my first reaction was to reach for the canopy.
But then I remembered that accident and put my arm back down and flew the plane.
My RV-12 flew fine with the canopy open, but it was a little windy. :-)
After climbing to a safe altitude and slowing down, I was able to get the canopy half latched.
The handle was under the roll bar at least. I would not try opening the canopy in flight though.
What if you get your fingers pinched between the handle and roll bar?