We have a 1790 & penetration is no problem on inner or outer rows, however we till our ground, though bean stubble is only field cultivated 1x.

Re. rocks, we have more than a few. We still use row cleaners in corn even though we're conventional till. One specific reason for the row cleaners is to kick rocks out of the row. However we remove them for bean planting. We also have unit-coulters. No problems w/rocks. We just finished 3rd full season w/1790. No penetration or unit problems. As a matter of fact, 2008 was absolutely trouble free re. the planter.

That's "here" anyway.