Mike,
Which Cokin filter system do you use, I was under the impression that they did not work well for lenses wider than 20mm, but seeing your pics I guess you have found a way to make it work.
Would a setup like this work?
Get a cheap 49mm filter,
Tiffen 49mm UV Protector Filter 49UVP B&H Photo Video remove glass.
Get a Lee 49mm wide angle adapter,
http://www.bhphotovideo.com/c/product/87140-REG/LEE_Filters_WAR049_Adapter_Ring_49mm.html I would hope this is just enough distance to get past the lens hood without creating vignette.
Do you think I could fit a 49mm to 67mm step up adapter instead of the 49mm tiffen filter. The reason being is that I have another lens with a 67mm filter size, so that way I could use the same Lee Adapter ring for both lenses.
Attach Lee Filter Holder
LEE Filters Foundation Kit FK B&H Photo Video with only 1 or 2 sets of filter holder blocks.
Then slide in what ever ND or ND Grad filter I wanted to use (HiTech, Lee, etc..)
I assume this could be done a little cheaper if I went with Cokin instead of Lee, right?
Thanks