A Douglas side with an average age of just 20 overcame stiff resistance at Oldershaw to bag a 22-15 win.
First half tries from Niall Killey, Bryn Snellgrove and Conor McCoghan saw Douglas 15-12 in front at half-time.
Snellgrove added another after the break which was converted by Tom Chamberlain and this was enough to seal the game.
Coward joins Rees in Milenco by Padgett's for this year's TT
He'll be riding for the team in new-look Sportbike class
Herbertson firing on all cylinders at this year's TT
34-year-old confirms Superbike machinery
New FC Isle of Man deal for Rick Holden?
Former Premier League star is open to talks about staying on as manager
Former minister urges talks to continue over IoM Sport funding
Budget shows 'significant investment' in infrastructure, says Allinson