Douglas are the Scratch League Champions.
They won Monday's title decider against close rivals Castletown 4-2.
Elsewhere, Mount Murray assistant professional Allyn Laing had to settle for second place again in the James Brearley Lancashire Open at Blackpool North Shore.
The former Castletown amateur was beaten in a play-off last year.
On Tuesday, he finished two shots behind Barry Taylor from Houghwood, despite a best-of-the-second round 67.
Laing is expected to be confirmed a Mount Murray head pro in October following Andy Dyson’s move to Ramsey.