I just saw this in a game and I think it should be changed.
Person 1 had Three cards and then eliminated person 2 who also had three cards. So person 1 now has six cards so he has to trade a set in. But with these six cards he actaully has 2 sets of matches so he is then able to cash both sets in at the same time resulting in quite a few men.
I think that you should only be able to cash in one set. That would put you below 5 cards in your hand and then they could trade them in next turn.
Did I explain that so you can understand it? And what do you think?