I have the gold SkyWatcher ED80 and a DSLR (similar sensor size to QHY8). Frustrated with the curvature/eggy stars as you mention, I've bought the WO Flattener IV. Did some initial testing
here the other night, but will be giving it a bit more of a serious workout this weekend. I'll certainly be posting results somewhere here, because if it doesn't work I'll be ropable, but if it does work I'll be ecstatic.