Just for the fun of it I went to Jackson's and did a little playing around.....

Beman ICS 340 @ 28" with 3 4" vanes and other wise standard ICS components with an 85gr head comes in at 404gr and an 8.1% FOC. Same thing with 400 shaft but the FOC pumps to 8.7%

I think that is a fair representation of a somewhat typical setup....exception being the head weight. Add longer vanes and/or wraps or dipped shafts and that back end gets aweful heavy in a hurry.....of course, most guys seem to be shooting 100gr or 125gr heads. Just some food for thought.