DISPROPORTIONAL, adjective Not having due proportion to something else; not having proportion or symmetry of parts; unsuitable in form or quantity; unequal; inadequate. A disproportional limb constitutes deformity in the body. The studies of youth should not be disproportional to their capacities. [This is the word which ought to be used for disproportionable.]
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI