Hey Jeff,
I agree that the vignetting can actually add to the image on some occasions. The LH-1 hood that I've been using looks like this;
http://www.bhphotovideo.com/c/produ...er_45BD217A
_LH_1_Rectangular_Metal_Lens.html
I bought it after noticing my fingers finding their way in front of the lens sometimes. 😉
Although I've been very happy with Capute One LE it does not have the lens correction feature that Epson PhotoRAW has and yes, I do correct for vignetting sometimes just not removing it completely.
I really doubt the small hood that comes with the 21mm caused the vignetting. Is yours the screw-mount or m-mount version lens?
Regardless, nice photo work on your part.