OHG missing forms

In OHG preterite-presents, not all of the forms are attested. For example, eigan, which is attested only in the present tense, and only the 2nd person in the singular indicative shows up that I can find.

I think only two -possibly three- preterite-present verbs seem to have past participles(I find hints that kunnan might have one, but nothing concrete yet.).

How should this be handled in these cases? Do we leave them blank; list the unattested but likely form(say, 2nd person singular indicative *anst beside 1st and 3rd an for unnan); or fill them in as if they were attested? Also, would they be conjugated regularly/irregularly in a module, or manually with the table template?

Showing the most likely reconstructed past form would probably be better than listing nothing at all. Grammars often do things like that. But the past participle could be left blank because it is probably missing for semantic reasons. Like in modern Dutch and German.

Okay, thank you.