I found that I had forgotten my side (main) latches once when I was half-way across a body of water that I didn't want to land in. The top latch was holding, but I slowed and my passenger and I leaned our elbows on the inside corners of the canopy and were able to pull it down far enough to get the latch engaged. I didn't record how slow I got, but I don't think I was down to 60 kts. As I recall, we did a climb/dive cycle to unload the canopy, leaned on the inside, and hit the latch. Remainder of flight was uneventful.