How to Create a 1280 x 960 project?

Cannot find a way to create a project from scratch in 4:3 HD apect ratio. I´ve tried adding a video from my Gopro, others created in imovie, photoshop, or quicktime; but always comes the window: "video properties are not recognized"

The workaround I found for another project was to create a bigger size frame, that contained the 1280 x 960 footage, and then cut the letterbox with compressor and exported just I wanted. Really time consuming because compressor is TREMENDOUSLY slow and buggy.

But on this new project I´m working with stills, and I need to see my 1280 x 960 frame inside fcpx, because many of the pictures move, zoom and pan; and if the workspace is bigger than final export, I´m driving blind.

Any help appreciated.

Thanks,

Pablo