Is there any reason why I can't modify a first position 11t shimano cassette cog (file down the bits that make it first position) to run in the second or third position? I don't use a full cassette on my bike and I really want the 11t.
If you are wondering why don't I just use it in the first positon as intended it's because I can't. The chain rubs on the seatstay.
*edit - All fixed. I put a spacer on the drive side axle and now the chain clears the seatstay.
No it would be fine, file them a bit, and put some spacers (like for single speed kits on full length freewheel body), and finally adjust the limit screws on the derailleur.