Replying to Boot problems

I´ve been using the teneighty boot for two seasons, third just started. The inside shoe is perfect but the shell have got bigger. When I bought them from a guy who used them for one season they were perfect. Now i cant get the two lowest clips tight enough. my heel wont stay still and that is not comfortable. I got the advice to glue a rubber sole under the inside shoe then the foot would be a bit higher and the problem would be solved. i tried that but my heel wont stay still even if I have two extra soles so it didnt work that good.
So Im now asking if somebody now if there is anything you can do about this or should I just get new boots?