Just curious, what would you do in a tip-over like the RV-4 or a lot of RV-8 fastbacks?
I have a side-opening fastback -8. Having already considered the matter (a recent trip included a lot of time over-water), I would jettison.
There's no golden ticket here, no sure thing. The canopy would offer some protection, but also some risk.
Popping the canopy by choice is somewhat different from an accidental deployment...an opportunity to duck before pulling the handle.
The canopy assembly is quite large and has a
lot of lift (aided by the gas strut), based on experimenting while doing a runup. I think it would get pretty far open before the piano hinge rips away, then I'd expect it to go outboard and up. The gas strut attachment is the wild card.
I see two kinds of ditching, shallow water and deep water. Shallow means the canopy will likely be against the bottom, thus impossible to open. I'd have to break it, while upside down with my head underwater. If flooded, it would be difficult to generate enough swing to break a canopy. If not flooded, it will be as soon as it breaks, and that will probably be long before I can make a hole big enough to escape. I do not think I could right myself in the confines of the RV-8 cockpit, as I'm just too tall.
I'm not sure about some aspects of a deep water ditching. I see the airplane floating momentarily until the wings flood, inverted, nose down, tail in the air. With leading edge or tip damage, flotation wouldn't last long. The cabin would be flooding, but I don't know how quickly. The canopy may be difficult to open until flooding complete.