On enwiki we have en:Template:Infobox3cols, which makes it possible to specify one label and two data cells on each row. This is used in quite a few sports-related infoboxes for career statistics, e.g. en:Template:Infobox AFL biography. Infobox3cols has about 150,000 transclusions on enwiki at the moment. Would it be possible to add support for another data cell so that infoboxes that use infobox3cols can be converted to Capiunto easily? I'm not aware of any infoboxes that use more than three columns, but I shall have another look around and report my findings.
Topic on Extension talk:Capiunto/Flow
It's been pointed out to me that infobox3cols actually allows four columns, despite its name. See en:Teddy Sheringham for an example of an infobox with the full four columns in use.