Time-Sert

Hello, this may have been covered before so if it has please point me in the right direction. Bought the time-sert 1210 set for my 2001 civic timing belt tensioner that stripped out during change. The kit comes with the 20mm insert, I have found that you will need the 14mm insert, for the insertion tool to pass through and lock in. Has anyone run into this issue before? Also, can you use a stainless steel insert or does it need no stainless.-TIA