I owned at one time a Wollensak Raptar 13/20/25 convertible and the combined elements did not cover 11X14". Almost, but there was some vignetting on the corners. I don't remember about the single elements but generally the coverage of the single elements is not more than that of the combined elements. You have a longer focal length but the actual angle of coverage is much less.
My understanding was that the Raptar is the coated version of the older Wollensak triple convertible.
mine is a velostigmat 1a ..
and it is on a 11x14 portrait camera that i use pretty often.
i have never had vignetting or coverage issues.
maybe they changed something between the change of names ?