I took a heavy duty down perssure system off my 7300.  It had 4 springs.  Max. down pressure I would recommend is #3 out of the 4 settings avaiable.  IF I used #4 those planter units would hardly move up and down at all.  It was like they were locked in place.  I did use it on #4 for a period of time.  It was to hard on the trash movers and I was loosing bearings because the load was to great on the bearings.  Happy planting.