Here's another little machine I built, from ground up.
You have the choice of 7 of 13 points to use, 7 being for initial ground breaking, and then the 13 for breaking the ground further.
The points are positioned on a 45 degree angle to help with penetration due to the light weight of the unit. A fair bit of design and testing went into this seeing as it is designed to be towed with a rideon.
It is fully height adjustable, from 2 inches above to 3 inches below ground level. The front row of points can be rotated by means of a lever mounted to the side. The force from digging isn't carried by this lever though, there are blocks mounted on the rear of the front beam that locate on the rear beam when the front beam is rotated. The points are made from Grade 8, 5/8 inch diameter bolts, so they shouldn't bend or wear out in a hurry.
It does take a bit of time to prepare the ground, but then it's not a farm impliment. I designed it to be used for preparing ground for lawn.
Oh yeah, please excuse the dirt stains!