i made a composition in Ae using 10 swf's that were created in flash at a resolution of 720x480 at 30fps. i wanted to create a bluray image, so i set the composition to 1920x1080 at 29.97fps. I then rendered it as a avi, quicktime and h.264-bluray format just to see which produced better results and i inserted it into an Encore composition and burned it. when i played the bluray disk on a bluray player using a 32inch screen, the picture was centered but very small- only about a third of the screen.
Honestly, I'm surprised you didn't rip a hole in the space-time continuum by bringing swf files into AE! haha. That usually creates all sorts of problems, that's if AE will even take them in the first place. First thing to do is convert them to an edit-friendly format (not h.264, swf, etc.). But to your question, "what am I doing wrong", aside from the swf files, it's hard to say since you haven't really told us much about your render settings or anything. Are they set to full resolution in the render queue? The formats AVI, quicktime and blu-ray don't really tell us much since there are all sorts of options within each