Have a Lexion F540 on a 585 combine.  Growing wheat, barley and canola.   Wheat and barley are usually partially to mostly lodged by harvest, and in recent years, all flat from snow.  This header does an amazing job of picking up everything, but an abysmal job of getting it into the feeder house in in a way that won't plug the feederhouse. 
In crop that is slightly standing still, it works fine.
In some directions, and a certain moisture levels it works great, but not when it is too hot and dry, or too tough.  
Have tried every adjustment I can think of.  Stripper set tight, auger as low as possible, no obstructions, full finger auger, tried all finger angles, and tried removing some or most fingers.  Header pitch feeder house, tried different angles, and different speeds.  Run it locked and unlocked, all reel positions and tooth angles.  Nothing helped much.
In dry conditions material piles up between auger and feeder house, in tough conditions, the feeder house backfeeds and plugs, or plugs without backfeeding.
Much worse when the crop is laying in certain directions.
fed almost flawlessly in heavy wet and green snowed on canola, but it is so tangled up, it drags itself in.  

I am advised that a Macdon flex draper probably is the answer, but really wouldn't want to give up on the full flex header in these conditions.  

Are there any other adjustments, or combination that might help?  I haven't tried changing table auger speedAnd modifications or attachments that could be added?

We have been discussing this on combine forum, but lots more people running flex heads here on NAT, so I wanted to ask here too.