I bought a pair of Zamberlan 996 Vioz GTX boots a few months ago. How long do these boots usually take to break in? I feel they fit well (one size down was definitely too small as my toe just touched the front of the shoe), but even on a 5k walk with lots of up and down they rub near the inside of the heel and cause blisters. Did approximately 10 walks so far (5-7km) and would expect things to get better by now, even though I realise that they’re a very stiff shoe. Tried double socks, insole, tighter lacing, nothing seems to help. Any tips?