Took a bit of fiddling but bending the barrel on an FX-400 would have been more grief for me than a half hour or so of trial and error with these mounts. The Sun Optics mount was a relatively cheap and simple solution.
My rifle had droop and I wanted to keep optical center. Problem solved.
Prior review with some comic relief (Matt Dawson, where are you now?) here: http://www.network54.com/Forum/79537/thread/1406680751