Sanskrit usages: vibhu vs. vyāpaka

Alessandro Graheli suggests me the following distinction between vibhu and vyāpaka:

vyāpāka means “all-pervasive”; vibhu is the consequence, as far as size is concerned, of such all-pervasiveness, hence its opposite is “madhyama” (of middle=normal size). I may suggest: “all-pervasive” and “infinitely-extended”. See also Laine, Journal of Indian Philosophy 1998.