i'll get you some pictures of mine in a bit . it's 4x4 wide and 3 tall I made it out of commercial square a/c duct some 30 odd years ago . it has been the best box I have ever owned and has
hauled coon hounds beagles , labs and you name it lol . it might weigh 50 pounds and is strong enough to rig dogs off the top or to support my 195 pound behind as of late lol . if you know some one in the commercial a/c buisness it wouldn't cost you very much to have one banged together .
Can you post some pictures