Instonians only need six points from their last three games to make certain of promotion to Division Two.
Clem Boyd's side bounced back from their first defeat of the season at Greystones with an empathic bonus point win over Ulster rivals Banbridge at Shaw's Bridge.
Inst remain second in the table a point behind leaders Seapoint who also claimed a maximum five points.
Inst face a crunch tie next time out at City of Derry but then have bottom club Connemara at home before finishing against struggling Barnhall. Boyd was happy with the 39-8 victory of Banbridge.
“That win gets us back on track and the boys responded well after the Greystones defeat,” he said. “We just kept the scoreboard ticking over, we now have a big match against Derry on the 26th March.”
Tries from winger David Parkhill and Ulster Ravens flanker David Bradford plus two penalties from full-back Scott Browne gave Inst a 16-8 half-time lead.
Prop Alan Whitten went over twice in the second half to secure the bonus point.
City of Derry breathed new life into their stuttering promotion bid with a 23-16 victory at Nenagh. Bevan Lynch's side had lost their last two games going into the trip to Tipperary.
They were made to battle hard by Nenagh but a late try from full-back Peter Henderson secured the points for Derry. The Judges Road club remain in the last automatic promotion place and are five points clear of Banbridge who left Shaw's Bridge empty handed.
Rainey are now only five points behind the Rifle Park club as they make a late bid to secure the play-off spot against the bottom club in Division Two.
Banbridge have two of their last three games on the road although they face Seapoint on the last day while the Old Boys only have one game at Hatrick Park.
Out-half Mark O'Connor was the hero at the finish, scoring all the points in the 19-17 win over Barnhall.
He converted his own try and kicked four penalties.
Ards virtually secured their senior status with a 34-32 win over Connemara at Hamilton Park.
The visitors managed two bonus points meaning Ards need a couple of points from their last three games to mathematically guarantee Division Three rugby next season.