I second Swingman's suggestion here. I used the approach (from the Klausz bench) of one large diameter short peg on the top of each trestle end, fit into shallow holes in the bottom of the top. The top is different from your average table top in that it has much greater mass, and is not going to move unless you very intentionally move it. The peg is enough to resist the lateral forces from planing, etc., which would otherwise make the top move.
Whatever you do, though, only one fixed-point attachment at each trestle (screw or peg). If you feel the need for a second attachment on each end (such as for moving by lifting from the top), make sure to allow for lateral movement at the second attachment point.