Screwed strips of 1"x2" across Longerons. Used a hammer to lightly tap the longeron strips flat and then snugged the screws. Note: I pilot drilled the holes and dry fit them. After I epoxied the longerons and went to put the 1"x2"s in place the screws wouldn't grip. So luckily I had some 2" screws handy. Lessons learned, when you dry fit the fixture, don't seat the screws all the way. You need to put them in to ensure you have proper alignment of both holes but leave a 1/2" or so showing on top.
