I understand that a 13 T needs the case to be filed down, in my case, I have already done some case modifications to make my 15mm bing sit better in the stock 12 square location.
It would be nice to see me have a 40 tooth and be able to get the 44 tooth for a replacement at some point as well.
As for the 35 uphill, thats because I made my own Sachs Estoril Sidebled w removable back bleed.