Im shooting 28.96% (or call it 29% efoc).
Beman Centershot 400's cut to 28.25" (i draw 28.00) with a 75 grain brass insert, 310 grain head, and 3 - 3.5" parabolic fletchings on the back, 10 grain nock. The calculator calls it 1 to 1.5% less than what the efoc really is when you actually balance the shaft on a knife blade and take real measurements.
Bareshafts fly great out to 25 yards. In fact, I can even shoot a bareshafted broadhead out to 15 yards quite well (dont try that with normal foc).