I took a moldboard plow off a small garden tractor and modified it to fit my ym1500.
It works great.
Here are some tips:
The angle of the plow as it engages the ground is critical, if the cutting edge is paralell with the ground - it bounces on the surface.
I have never got too agressive with mine, but i would assume it would want to keep cutting deeper, and deeper.
I found that an angle just steep enough to get the plow to cut into the ground works GREAT.
Also the distance between the coulter and the plow seem to have a lot to do with how deep the plow cuts. (the greater the distance, the deeper the cut.)
The top link adjusts the angle of the plow. I will try and post mine in the near future.
Anyway, plowed just over 1.5 acres in only a few hours.