I came to like Boxleitner a lot from his work on B5. But personally I've always seen and heard Burt Reynold's as Vaughn.
Think of Burt Reynold's from Cannonball Run
and Cannonball Run II
and you'll soon see it's not a good fit (IMHO).
Have a look at this image of Boxleitner and you'll see he fits as Vaughn very well.