Yes, it looks like you have another step which is appending a two-digit sequence number to your data. This is not necessary.
OPTION COPY
INREC OVERLAY=(26:SEQNUM,1,BI,START=1,RESTART=(1,11),
26:26,1,CHANGE=(1,
X'01',C'A',
X'02',C'B',
X'03',C'C',
X'04',C'D',
X'05',C'E',
X'06',C'F',
X'07',C'G'))
This gives you:
50015662008 A0001-IBW82U20150702
50015662008 B0001-IBVWME20150702
50015662008 C0001-IBVXME20150702
50015662008 D0001-IBVYME20150702
50015662001 A0001-IBVAME20150702
50015662001 B0001-IBVBME20150702
50015662001 C0001-IBVBME20150702