Perfect box joints

This is part of a speaker project made out of walnut. It’s taking me a long time to complete because I only have routers to work with. All boards were straightened and joint using a router. Another month or so, the boxes should be complete. The X-Over design and driver measurements will take another 3-6 moths to complete.
I’ve never tackled boxes this big before so I had a heck of a time trying to cut straight lines due to flexing of the straight edge. 48.5 x 18 x 10.5.