JJ, I'm running a 500 series head with a new SCH system installed upside down. No problem with pushing trash during the day but as soon as it starts to get damp in the evening I have a bit of trouble in some no-till fields. My experience is that the trash starts to buildup back at the skid plates and not at that guards though so things like angle of the knife, spring tension and condition of your poly are things I would check. We have been blessed with excellent harvesting conditions so far this year and the upside down arrangement has been working well but I can see that in not so perfect conditions (like last year) it may not work quite as well. As far as shaving the ground it can't be beat.