
Hi GG, you don't say what breed your puppy is, but it's very normal, in most breeds, for 6 month old pups to be loose in front and everywhere else. At 6 months they are just babies that will take time to mature and tighten up, all over.
One of my breeds is the Irish Setter, and at 6 months they seem to have no co-ordination, the legs are flailing about all over the place when they move. Very loose in front.
Pasterns also take time to strengthen, road walking helps, but you should never over excercise a puppy. You can't rush maturity, so you shouldn't try. It'll come with time.