Built Up Sheeting technique
What I do is similar to all of these. I CA the sheet to the LE and wet the top, then add wood glue to the ribs, BUT leave about a 1/2" gap near the center. Then put a drop of Medium CA in all of those gaps, and CA the spar. Now, fold it over and I hold it down with a long level that I have (Anything long and straight will do) for about 30 seconds, and it's good to go.
Note* The only reason I use the wood glue is to give myself more working time, and to cut down on the expense of CA.