OP was going to purchase new panels rated at over 400W. When the sun is positioned 90* perpendicular to the panels, the max production will occur. It appears your experience with these devices falls short of expectations, but from a safety standpoint, you must base recommendations on printed specifications.
As for the over paneling, if OP can find documentation from the manufacturer supporting that use, then it should be able to do so. I found a manual that was missing that particular information (or perhaps was in a different place). It seems documentation does exist to support using up to 3120W for this model. Just ensure it's from the actual manufacturer and not just a seller on Amazon (the screen grab looks professional, and for a diy weekend warrior it's probably acceptable).
