Components For My Ideal Seeder

I feel I am getting a good grasp on the design of good disc assemblies. It will need to have:

1. A double offset disc of two differing sizes.
2. Have a small seed firmer wheel.
3. The depth gauge needs to be independent of press wheel ( put on front discs).The depth wheel needs to hold the soil in place as the blade pulls from the soil.
4. Furrow closer e.g. Star or cast wheel.
In addition to this, Dwayne Beck given some comments regarding the assembly attachment style:
A. The JD and similar have radial attachment which means the angle of attack is correct for only one spot in its travel.
B. The parallel (or parallelogram) linkage has the proper angle of attack as long as the frame of the implement is parallel to the soil surface (very level fields).
C. The walking beam attachment has the proper angle of attack at almost all times.