A picture would be appreciated aldot, to help people who look at this thread in future. We don't know whether there was a design change between your mower and Dave's, or perhaps one or the other was modified after it was made. Since your trim heights are now the same at the front and rear of the mower, it seems the idler is not necessary when you have a new chain. It also seems the previous owner of your mower probably pushed it quite a bit in continuing to use a worn-out chain.
