I am designing a tractor implement for harvesting root crops. Similar to this one here, but stronger construction with cutting discs in front of it to prevent weed jam. These images will help you understand my question. The whole implement is 1400mm wide and the pipe at angle is 200mm long relative to x axis.
The main frame has 2 square pipes welded together at 45 degree angle at each side. The pipes are 120x120mm(4 3/4"x4 3/4") with wall thickness 8mm(0.315"). I was sceptical about using butt joint so I put a 15mm(5/8") steel plate between pipes. Now the pipes are welded with a fillet weld (at 90°, 45° and 135°). I'd like to hear some expert or practitioner opinion on how structurally stable welding pipes in such arrangement is with respect to flat pipe without any welds. The forces will act on the sides, that are just 20cm(8") from the three point hitch arms so the leverage is pretty small.