Video & progressive download

Hi there,
at first I would like to ask if it makes any sens to set “buffertime” if I’m using progressive download for video?
The second thing is that for my video player I’m using the code beneath to preload half of the video file and let it resume in that moment.

private function onStatus(nse:NetStatusEvent):void {
            if (nse.info.code == "NetStream.Play.Start") {
                stream.pause();
                stream.seek(0);
                if (stream.bytesLoaded >= (stream.bytesTotal / 2)) {
                    stream.resume();
                }
            }

The problem is that on my website it plays the file but only after its fully loaded.
thanks.