vkernus,
I've had 3 Sig SE's, all with over at least 200 flights on them. You'll find here on this forum that this method of securing the wings is just fine, and will hold the wings together just fine. There are a few tweaks that people use, but the basic idea of the 2 J-hooks works just fine. When I assembled mine I installed the J-hooks before sheeting the wings, this let me put a nut (with red thread lock) on the end of the J-hook. This will ensure that it won't pull out of the wood (which is a weakness in the wood and not in the design). The other thing I do with mine is I use a zip tie to hold the 2 hooks together. I can do this because I transport my plane to the field assembled, so I don't have to worry about putting the plane together at the field. But a couple of #64 rubber bands will do just fine.

This design works because there just isn't a lot of linear force pulling the wings apart from each other. The main stresses on the wing are absorbed by the aluminum wing tube, and the use of rubber bands (or zip ties) is more than enough to hold the two wing halves together.