Meadow Pipit

Following discussion last year on ageing spring Meadow Pipit (& pics), 5 out of 6 ringed this morning were clearly 2CY on the basis of retained juvenile greater coverts. The other was an adult (all coverts, tail shape etc), but cautiously left as a '4' The 8 caught this morning exhibited a wide variety of spring plumage options 1) 2 x all feathers fresh adult-type, including all coverts and perceived adult-type tail 2) one with e.g. a mixture of old adult-type and new (adult-type) median coverts and perceived adult-type tail 3) one with e.g. a full set of 2CY median coverts and 1CY/2CY tail 4) 4 with a mixture of old 2CY and new adult-type median coverts and 1CY/2CY tail Obviously 3) & 4) are '5's. However, can 2) be definitely assigned as a '6'? Especially as the older feathers look too worn to be a result of a two-stage replacement of juvenile median coverts during late autumn/winter. Am I too cautious ageing 1) & 2) as 'probable adult' but safer to call '4's?