I bought a Gehl 1075 with processor, 2 row corn head and hay head a few years back and it was working great.  I put four more kinves in it after I got it because the previous owner only ran 4 knives in corn for whatever reason.  When chopping corn in 2011, one of the knives came loose and crashed into the rear of the chamber around the cutterhead (not the shear bar) and damaged the spiders that hold the blades down.  I brought it into the local dealer the next spring and they ended up having to replace two of the spiders, the bearings, and the one knive that was smashed.  I had a good used knife with approximately the same wear on it as the ones in there, so they used that.  When I got it back, I sharpened the knives and noticed that the stone seemed to be jumping as I was grinding.  I was in a hurry and just set the shear bar and started chopping.  It chopped like crap.  There was anything from 3/8" pieces to 18" pieces in the wagon.  I only chopped a few acres of first crop clover and ended up baling the rest of the hay, so I didn't use it much last year.  This year, I took a better look at it and noticed that two knives weren't being sharpened like the rest.  One was not being sharpened at all, and the other had a gap in it that wasn't being sharpened.  I figured that this was due to the fact that the shop found that the previous owner had smashed up the cutterhead before us and had patched it together to make it work so he could trade it off.  There was much more damage than just the one knife we had come loose could have caused.  That's why they ened up having to rebuild the whole cutterhead.  Due to the spiders being twisted already, the knives weren't sitting square and had been sharpened differently than they were now that they are in the correct position.  I spent time this spring sharpening the knives until they were in a perfect drum again, and set up the cutterbar.  The tractor handles the chopper much better now, but it still chops like crap.  I still have a ton of long feed in the wagon.  Some of it looks like it wasn't even touched by the cutterhead.  What am I doing wrong?  I have the cutterbar so close that if I even move the adjustment bolts a hair it starts tapping.  The cutterbar looked straight when I pulled it in the fall of 2011, and my straightedge showed it to be so.  Should I try replacing it to see?  They are pretty expensive to just replace it on a whim, and the other side hasn't been used yet (I replaced it when I put the new knives on in 2010.  Any suggestions?  Any ideas?  This is really getting frustrating.