it some what depends on what your wanting to cultivate,
at least in my thinking a cultivator is made to work strips of the soil leaving the plant that is desired untouched,
most three point cultivators I am familiar with are basically a tool bar, that can accept different shanks and shovels sweeps points or even disks to work the ground around a row of plants, some tool bars are two and three bars deep,
when I did corn I had one I made two rows deep and use straight shanks and made my own shovels out of sweeps by cutting off one of the wings on the sweep, and then pointed them so they would plow some,
see some with multiply tools handing off of swinging bars hanging out the back of the machine with shovels and sweep type and a disk all working the same row area, some ran on a gage wheel,
so I think first of all what are you trying to cultivate,
there are other mounted machines for working the general area, and normally you will need a few Row of bars so it does not become a hay rake and plug up, such as a mounted (three point) ch isle,
as far a pictures of three point cultivators, take a look at the google images,
three point cultivators - Google Search
I made a ripper so to speak, with a 4x4 bar and welded up a mount for the three point and put about 4 or 5 chisel shanks on it I had used on another machine and was no longer using, with chisels points, (it is the width of the tractor) and I use it when digging dirt with the bucket or if I am using the is mover on the other tractor, to break up the soil to ease the load on the bucket and the tractor,
the ripper I made is similar to this picture but with one more ripper point,
http://www.cih.com.au/images/products/3pl_tb250ripper.jpg
most AG tractors and loaders are not designed for dirt moving, most are only rated for manure loads, (look at an AG tractor and loader and look at a commercial loader on a back hoe or simular tractor that is designed for earth moving,
Please and Thanks ahead of time