Short focus

[Nuce]

My 100-400 IS seems to be focusing about 6 inches short of the intended subject.  Is there adjustments in the 7D that can help with that?

[7D5D]

Yes.  The 7D allows AFMA (AF Micro Adjusting).  C.Fn. III - 5. 

For proper results you will need a tool to properly test your lens:

I prefer and use FoCal.  Other measuring tools are LensAlign (which I do not recommend) and Spyder LensCal.

Some  useful links:

http://www.northlight-images.co.uk/article_pages/cameras/1ds3_af_micoadjustment.html

http://www.the-digital-picture.com/Photography-Tips/AF-Microadjustment-Tips.aspx

If you want to adjust your lens without any tool you can try this:

http://www.dgrin.com/showthread.php?t=116078