I fly my RV8 with the canopy open about 5 inches at speeds up to 115 knots.
I also have an extra bulkhead top positioned under the rear slider block at that position to keep the turtledeck skin from deflecting. There is a lot of downward pressure on the canopy inflight.
I believe there is a longitudinal rib under the 6,7,9 slider track that would serve the same purpose as my extra bulkhead top.