RE: Best Basswood Glue
Since the biggest problem with these sorts of joints on WWI fuselages is sheering off (rather than strength in a "pull apart" direction) it seems like one simple solution would be to drill 2 or 3 small "starter holes in both faces of the joint. Then either epoxy or titebond would go into the holes and when hardened help prevent the sticks from sheering off. Of course, the best solution might be to use gussets on all the joints.
What did Del do on his GTM DrI? That seems to have work out well!