
it depends if it is a fault with his tail set or his tail carriage. if his tail is set to high causing the tight tail, then this wont resolve. if his tail set is ok, but he is carriage is wrong he may settle and carry it correctly when older. my youngest who is 15 months gets very excited in the ring and he will carry his tail a bit tight, but at home it is not as bad. he has done ok in the ring as a pup, gaining a couple of 1sts, 2nds and reserves, it depends on the judge and how the severe the fault.
have a look at these, they may help
breed standard breed standard 2 kelly