Zen Nudist: Apparently I wrote too quickly. I cannot check the matter further now, but if I understand correctly the critical apparatus of Nestle-Aland 4th ed. all the uncials (such as Codices Sinaiticus and Alexandrinus) seem to have it in full spelling, with spelling variants (as well as the 616 variant in Codex Ephraemi rescriptus). However, papyrus P47 which is older (3rd century) seems to have it in numeral letters (kh-x-s), like in the much later byzantine tradition...
If I find something more I'll let you know (unless someone else comes up with better information). Btw, could you give me the link to your on-line texts?