Well, a nice thing about Tapas is that it has no rule on cross-posting your comic to other places, like other comics platforms or a website, so building a site using something like a wordpress template, or cross-posting somewhere like Comic Fury or The Duck, which are smaller, but have audiences that skew older, are options.
You could try seeing if you can make a Tapas-friendly version by trying to make the speech bubbles and text bigger (not always easy, depends on how much space the art leaves you with), or like you said, putting the panels large and in vertical format, which would also work.