I use to run flex heads cutting wheat for years.Even bolted up it doesn't feed as good as a rigid head.If you have to run the flex it feeds the best with the auger set in the upper to middle position,and with the auger as far back as you can get it..It has to be almost hitting the striper plate.Sometimes it does hit,depending on how long you let it sit in the sun.If it does hit when starting out,don't worry,it will come out of it.