Try the reverse bars, might work. We add , weld, a scraper to the end of two opposite paddles, angled forward to keep this from happening. If you do and it works let us know.
Straw has a very hard time moving over without the combination of forward rasp bar and helical. When I ran forward bars to end of rotor at four locations I left the rasp bar about an inch from edge of backup bar. Also I don't have the helical extended any closer than about 4" from stop sign. Be sure you have the discharge bars that come to about an inch from discharge. Earlier large rotors had about two inches to stop sign. I heard of a guy that extended all eight bars to the end and unsure what he did with helicals but he bowed the stop sign. Either of your ideas may work just fine also.