I was SOOO stoked to get my new Fluid Motion hard shell yesterday - but have an issue with the liner. I ordered the size 3 liner which is supposed to be their large (10.5-12) - but the liner is SO short from heel to toe. My toes are crammed at the front. I am nervous that if I heat mold the liner and it does not stretch enough that I will be stuck with it. How much do these stretch front to back?