i dont know why copy/paste would be faster, and safer, than drag n drop,
but in my experience it has been.
i've had FCP crash on me if the drag was too big.
that was a while back, but since then, i've restricted myself to copy/paste.
(well, i drag from the browser to the timeline, but i copy/paste going the other way)
i wondered if it had gotten better, but seems not.
interesting about the project file sizes, i hadn't noticed that.
(not saying it didn't happen, just that i didn't notice)
nick