Thanks Stefan for screenshots and screencast! For Proxy, could you use .mov, for example, instead of JPEG Sequence (or other type of sequence), please? In your screencast at 2:11 you are dragging and dropping the clip from Resources/MEDIA when Proxy is enabled! Like said in my previous post, when Proxy is Enabled you MUST to use Resources/PROXY. You are changing the Z value of the Camera tool because you have used Resources/MEDIA instead of Resources/Proxy when Proxy is Enabled.
Is there any technical reason not to have the viewer play any clip in the *media's* resolution. Regardless of proxy or project setup? Have have you tried "my" Workflow? May be it is good also for you.
PS: I always use Proxy and it always works right! Pay attemption becouse some plugins, like Title, are not developed for Proxy. IgorBeg