Originally Posted by Sleddgracer
the screws have to be long enough that the 'wings' have enough room to spring open once they are through the floor - if they are flipping open there is no way they can't tighten up - just takes a lot of turns to take up the slack - if the wings don't flip open, they won't work
He's not talking about moly bolts. He's referring to the drill flutes on the screw tip.
Why is it important for the screw thread to grip the wood? If you have a sturdy base for the screw and the head is big enough that's all that's needed.