when ever I have joined wings I use 30 min. epoxy on the joiners,the ply pieces that link the spars in each wing half.
I am not famillar with Sig Bond I would assume its there adhesive brand,having used carpenters wood glue,mainly Titebond, for years I would think it is plenty strong for joining the halves as well,keep in mind more glue doesn't make a better joint, enough adhesive to glue the wood and a good clamp job is the best way loading up on epoxy just adds extra weight not strength if your joint is tight you will have a strong wing in the end.