No, no problem at all! This is all really helpful for me-your projects spurred me to do some work of my own on a Mac and no one else I know of really knows anything about Mac conversions etc. with Streamclip and other software.
So...using NTSC standards of 720x480 for instance I would need to crop about 37.5 pixels off the top and bottom if I didn't crop any off the left and right of the frame. Thus about 720x405. Does this sound at all right or am I totally off base?