With the aft portion of the deck supports completed, we were raring to get some of the Trex decking laid down. And lay it we did. ;-) 2 decking screws at each Trex/4x4 intersection.
We used 1/2" bolts as spacers to maintain the gap;
a ratcheting motorcycle tie-down came in handy to pull any skewed Trex back into shape.