Thanks Randy.
On Dreamhost VPS, I got it going by pointing the NS records to DH. Then creating a mirror on that domain name to the WPMU main domain installation. Just pointing the A record to the IP address of the Dreamhost VPS did not resolve WPMU domain mapping.
It would have been easier if it’s a dedicated server using CPanel, but wrestling with VPS is like shared hosting.
Anyway, thank you for taking the time to answer the question. Cheers mate ??
Victor