I'm trying to use anamorphic pal clips in a HD storyline, but the spatial conform feature just allow a fit or fill approach, cropping the image and not deanamorphising. I got a workaround by using distort, but need to apply it to a bunch of clips, and it only works in the timeline, not in the event library... Some kind of conform command, ala after effects will be quite useful.
I'd say the easiest thing would be to fix one clip in the timeline then copy and paste the attributes (Cmd/C then Cmd/Opt/V) to the other clips that need fixing. Same as did in FCP7, but note that all properties get pasted and you can't choose which, so do it before you've added any specific filters to your first clip.
I think that this spatial conform option is not completely finished. I am also trying to tackle this problem. Not for a real project yet, but without it, the application is even less usefull than it already appeared to be.
ProRes material that is run via Compressor with a 16x9 tag will work in an anamorphic project, but I tried the same thing with the IMX codec, because we have a lot of IMX material on our server and then it didn't work. (I don't want to re-transcode all our material anyway, but it was just a test to see if it would work).
When done with a ProRes clip, FCPX also did not have to render the timeline, just as in FCP 7 was the case. If you use distort it will need to render.
Dropping an SD PAL ProRes clip which has been transcoded with Compressor with a proper 16x9 tag will also scale correctly in am HD project, it will need to render for the upscaling though.