Question

Is the size of one's tallit merely a matter of custom or preference? Is it inappropriate or ridiculous for an adult (6 foot) to wear his bar-mitzvah tallit?

Answer

There is a law is that the minimum tallit should be sufficiently large to clothe a child old enough to stand and walk (Orach Hayim 16:1).

I do agree that for the sake of propriety and respect you are correct that one should wear a tallit appropriate to one's physical stature. I have always encouraged parents to purchase a tallit for the Bar or Bat Mitzvah that will still be appropriate for them as they mature and grow to their adult proportions.

There are those who become anxious with a large tallit – how does one put it on, wear it, “flip” up the corners on the shoulder, gather the tzitzit? And so, it is easier to wear the “form-fitting” shawl style, although the history of the tallit reflects a four-cornered garment that would have had two tzitzit in front of our body and two at our back, such as the large tallit provides.

You can also purchase a large “form-fitting” tallit that is modern and very attractive, that doesn't make someone look “ridiculous” at worship.

On the other hand, frequently there is such meaning in our Jewish symbols and possessions that we hold them, use them, and even wear them (e.g. a kipah, a tallit, a magen david or Jewish star) because of their origin and/or associated memories and personalities). Perhaps the man to whom you are referring is one of those who associates wonderful memories and meaning with that tallit.