"hardly familiar" is correct and usable in written English.
You can use it to emphasize that something is not well-known or that you have very little knowledge of something. For example: "I was hardly familiar with the concept before the lecture."
He's unknown here, hardly familiar in America.
Midway through its first season, the stadium is hardly familiar to the home teams.
But people with close knowledge of the search say Mr. Leventhal is hardly familiar with the functioning of the school system, and is still getting an education.
Well, one is hardly familiar with John Wesley's sermons, but I do know that to put George W. Bush's prose next to Hemingway's is equal to saying that Jackie Susann is right up there with Jane Austen.
The youngest generation of union members is hardly familiar with the process because labor has not shepherded its flocks to the caucuses since 1984, the last time the A.F.L.-C.I.O.
But actually going through the process has been a bit tricky — users had to deal with Facebook's developer app and API keys, which is hardly familiar territory for the vast majority of Facebook users (though many made it through the process anyway).
Unlike alcohol's blunt and blatant outward manifestations, its subjective effects, though hardly less familiar, defy exact depiction.
The Robomow has a manual mode, but it is hardly the familiar push mowing of the past.
American audiences may be hardly more familiar than Chinese ones with the complicated dynastic politics of England in the fourteenth and fifteenth centuries.
Not only did Mr. Bloomberg mostly avoid two favorite topics, Wall Street and national politics, he also tried to be a bit self-deprecating — hardly a familiar character trait — by opening with a light-hearted video of the Staten Island groundhog that bit his finger in 2009.
This should hardly strike anyone familiar with this city and the people who inhabit it as unusual.
