hi all- love all the information that is found here. new to large format, i've got a horseman 4x5 lxc and just got a schneider 90mm 4.5 s.a. and need to get a recessed lens boards for iy. i've found several on ebay, a 27mm and a 44mm.what's the difference in function?my guess is the 27mm will work fine, but thought i'd ask those that know.thanks everyone!! daryl kelley