I use my 210 SSXL quite a bit. It may in fact need the center filter, but I don't use one. If anything I like the fall off on the edges. I focus it at 7 feet and then stop it down to f/64 for hyper-focal. I shot the horseshoe bend down in Page Az. (funny story on that one for the LF Forum BTW) I used my 12x20 and the prints are some of my more recent favorites. Frankly, I would give up my 12x20 if I didn't have such a lens.

Cheers,