I second this request: please properly support the SimConnect simulation variables (read and write) where possible. And given the fact that even the Corsair (which according to the developer uses a lot of „custom code/local variables) is properly reporting CANOPY OPEN (is it also writeable?) it seems that it is possible to use it, even with enabled „stress damage“.
And yes, weeks ago when I asked that exact same question whether the Corsair would support CANOPY OPEN the argument with the damage system was given as an argument against it (but not sure anymore if that answer came from the developer itself). But it now seems that there is a way around the default damage system when using CANOPY OPEN (and flying with an open canopy which slides backwards).
Also refer to:
(The given example is with another aircraft, but it illustrates the usage of the Simvar Watcher which comes with the SDK)