I have fairly well sussed out the design for a twin leg one for my NH 45hp. I made a heavy duty box last year for picking up windrowed stones. I will use the box for weight. You need some to get depth, and I had originally intended to make a frame and use concrete posts and/or blocks which I have lying around, but decided the box already had a lot of weight and it can be filled with anything if more weight is necessary. I am using 20mm x 100mm as the shank - call it threequarter by 4 inch, and will weld a triangle on the bottom to replicate a curved shank, ie the bottom of the shank will be 4" in front of the main part of the shank. I will then use 3" angle iron to form wings, angled about 20º from the horizontal - just enough to give a wee bit shatter and lift. The same angle iron will be used to form the carriers for the shanks, and welded to the front of the box immediately behind the centre of each rear wheel. I will use a single hole fixing through the angle iron for the shanks. The force against the shank points will attempt to push the points backwards, but the box will prevent this happening. I will drill the fixing holes (20mm and using top link pins to hold the shanks in position) at 6" apart so that I can increase the depth by 6" at each pass. I do not think I will be able to take more than this on each pass. My maximum clearance from ground to the base of the box is 23", but by having adjustable depth shanks, I should be able to increase the subsoiling depth by pulling the shanks into the ground, raising the box to the next hole and going again. I need to subsoil in advance of planting olives and would like about 30"if I can get it. I have not yet decided whether to partially cut through the top link pins so that they will act as shear pins. Old McDonald.