I've had a similar experience with female betta and male guppies. I had them together for 5 minutes at the most (while changing around tanks). When I went to check on them, the female betta was locked onto the guppy's caudal fin and wouldn't initially let go! She made his spine really crooked with a large kink in it. I wouldn't recommend doing what you suggest, as I figure the male bettas would be even more cruel!
-Ian