Its not rocket science, but some hydraulic and geometry knowledge is required. A solid mounting location that ties as much of the tractor together as possible. Proper cylinder sizing. Hoses, joystick valve.
My only snippet is when welding fish plates, or braces, the braces need to be rounded, not square. Complete weld. This is common practice in structual fabrication and the first thing we learned going for our "R" stamp in welding. If its square, it will be weak along the welded joint whereas a rounded plate is stronger and provides far more strength.