I didn't glue them, and only the rotating arm joint in the Redemptor gave me any trouble. Both that I've built had no problems getting the front plates to stay in the open or closed position just with friction fit.
A little trick is to rough up the surface (in the machinist world there's a process called knurling that's used for tightening fits as a quick fix). Then paint. Keep adding paint layers until it's maybe just a little tighter fit than you'd like, because it'll wear.
Another trick I've used is to wedge some blu-
tac into the joint.
Still another fix is to use Sprue-Goo (this is a made up name

). Look up the Vince Venturella video -- it's essentially extra sprue plastic mixed 1 to 1 with tamiya extra thin (or any other extra thin plastic cement). You can then brush it on and essentially you are "painting" on extra plastic. This stuff is the ultimate gap filler as well. Anyway, you can use this to build up the joint surfaces for a tighter fit.