The first try came on 15 minutes for the holders when the Inst pack wore down the Methody defence before scrum-half Rhys O'Donnell sniped over from close range. Hume made light of the wind, converting magnificently from the sideline.
Inst's second try came on 23 minutes courtesy of a perfectly executed rolling maul; lock David McCann touching down over the whitewash to open a 12-0 lead.
A minute later Methody out-half Armstrong made a rare break into the Inst 22 but his offload to Kerr was judged to have gone forward. Methody did charge down as Inst attempted to clear but were then penalised for going over the top when Michael Lowry cleaned up the loose ball.
Methody continued to dominate field position for the remainder of the half and were rewarded with a try on 34 minutes. After several phases of pick and drives from the Methody forwards, play was switched from right to left for winger Chris Larmour to dive over in the corner. Kerr's conversion attempt was struck well but drifted just wide, leaving it 12-5 at the interval in favour of Inst.
Both sides were temporarily reduced to 14 men in the opening 10 minutes of the second half with Kerr then Hume both seeing yellow for high tackles, but it was Methody who made the early ground. It looked like Larmour was in for another try on 47 minutes but he was denied by a superb combination tackle from fullback Joseph Finnegan and captain Lowry as he drove for the corner; the Inst skipper unfortunately picking up a game-ending injury in the process.
Methody continued to control possession inside their opponent's half and when Inst were penalised at the breakdown inside the 22 Kerr gratefully accepted the simple penalty on 57 minutes, closing the deficit to 12-8, as the forecasted rain finally started to come in.
The score seemed to spark Inst back into life as they piled wave after wave of pressure on to the Methody defence deep inside the 22 but the ball was eventually knocked forward. Methody chose to try and run the ball out from the resulting scrum but were forced down behind their own try line. However, Inst were unable to capitalise on the 5m put-in as the ball was knocked forward from the back of the scrum.
Once again Methody neglected the option to kick and the Inst pressure contained their opponents inside their 22, where they turned over possession once more with the game entering the final minutes.
Inst used all their experience in the closing stages, holding on to possession in close quarters as the clock ticked past the 70 minute mark, before the ball was booted into the grandstand to spark the winning celebrations.
Tries: Rhys O'Donnell, David McCann
Cons: James Hume
(15-9): Joseph Finnegan, Zak Davidson, James Hume, David Lyttle, Niall Armstrong, Michael Lowry (Capt), Rhys O'Donnell;
(1-8): Callum Reid, Neil Saulters, Matthew Nelson, Dermot Wallace, David McCann, Patrick Finnegan, Charlie Cloke, Yasser Omar.
Replacements (16-23): Connor McCormick, Pierce McLernon (for Wallace 48), Ethan Sloan, Bailey Gribben for (Nelson 55), Ethan Field (for McCann 66), Angus Adair (for Cloke 59), Robin McIlveen (for O'Donnell 68), Sam Fryers (for Lowry 47).
Tries: Chris Larmour
Pens: Paul Kerr
(15-9): Kane Doherty, Ethan McIlroy, James McConnell, Paul Kerr, Chris Larmour, Thomas Armstrong, Johnny Jordan;
(1-8): Daire Morelli, Josh Trainor, Ben Crangle, Jonah Bingham, Hugh Gibbons, Cameron Kelly, Matty Loane (Capt), Thomas Gallagher.
Replacements (16-23): Calum Conn, Emmanuel Gentry, Conor Fletcher, Kevin McNaboe (for Gallagher 68), Conor Kelly, Matthew Neill, Louis Millar (for McIlroy 66), Louis Lowry.