pick a length of chain that is a multiple of 6.35mm that’s close to 0,0. This
will have a tooth on the sprocket at 12 o’clock. mark the link that’s on this
now go into settings and change the value from 1651mm to whatever this length
now when your chains get messed up, you just need to set the sprocket to have a
tooth at 12 o’clock and use the option to set the chain lengths.
this is going to be far more accurate than determining that your sled is exactly
centered in your circle.
but you could find what the chain lengths are when it’s exactly centered and
then use the existing mechanism to set the chain lengths to that.