Southern Nomads beat Vagabonds B 36-5 to maintain their lead at the top of the Shimmin Wilson Manx Shield.
Dave Caldwell, Harry Brereton, Rob Keelan, Glen Buckley, Conor Stephens and Steve McHugh all picked up tries for the defending champions, with Duncan Miller adding three conversions for a result which effectively ends Vagas’ title hopes.
Ramsey B kept themselves in the hunt with a 49-12 win over Emerging Nomads at Mooragh Park.
Rory Nicholson, Henry Doran and Connor Cracknell both scored two for Ramsey with additional tries coming from Kyle Kenyon, Henry Swithinbank and Dave Millard, plus two conversions from Garry Vernon.
Nomads picked up consolation tries from Dave Edge and Michael Craine, with Edge converting his own score.
Castletown raced into a 15-0 lead at Poulsom Park before Douglas pulled them back to run out 41-20 winners.
Tries from Mike Condra, Billy Hanrahan and James Jones put Town ahead.
Douglas hit back via Noel Capewell, Paul Gale, Joe Whitelegg and Liam King to lead 26-15 at the break.
In the second half, further tries from Mark Dimsdale and Nathan Pierce sealed the result before Barry Irvine picked up a late consolation for Town.