Although this would be somewhat of a radical fix, I wonder if some of the baffling should be removed if you're always going to be letting the grass get as long as you do. With my Woods RFM, there is very little baffling - actually only a little bit behind the center blade and the far left blade. All the debris if pushed to the right side but that blade has no baffle, however, there is a side cover, so the mower essentially acts as a rear discharge. Woods used to sell a "mulching" kit for the deck which included all the baffles, but I think that would just cause problems like you're encountering. FYI, my 46" Craftsman deck does the same as you've noted when the grass gets too long or we mow too fast.