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Champions Maidstone were given a guard of honour but it was Welling’s day as the Wings secured safety.
The Stones, back in action 48 hours after clinching the National South title, saw their eight-match winning streak halted as Warren Feeney's side got the win they needed to stay up with a game to spare.
Harvey Bradbury opened the scoring for Welling, with Hady Ghandour levelling after the break.
Bradley Stevenson restored the lead and Bradbury added a late third before Joe Ellul scored Maidstone's second at the death.
Victory for Welling, coupled with Billericay's defeat by Ebbsfleet, keeps the Wings in the division.
Hakan Hayrettin - sporting the Maidstone scarf he picked up during Saturday night’s title celebrations - made four changes for the Bank Holiday Monday clash at Park View Road.
Jack Barham (toe) missed out through injury, meaning a start for Ghandour, there was a first league start for winger TT Walters, while goalkeeper Yusuf Mersin and midfielder Johl Powell also returned.
Twelve-hundred Stones fans were in party mood with the championship in the bag - nothing was going to spoil their day - but there was plenty riding on the game for Welling.
It was clear on the touchline Hayrettin and No.2 Terry Harris were very much bothered about the result but the visitors didn’t hit the heights of the winning run that took them to the title.
They had their moments, Walters looking bright down the left early on and Sam Corne buzzing about in midfield, but Welling looked far more assured defensively, left-back Chi Ezennolim particularly impressive, than they had done in the 4-1 defeat at the Gallagher over Christmas.
Big strikers Bradbury and Dipo Akinyemi also looked alert pouncing on uncharacteristic mistakes in the Stones defence.
Chances-wise, for Maidstone, George Fowler saw an early header from a corner held by Coniah Boyce-Clarke and Walters glanced wide from a Christie Pattisson cross.
Welling were in on the quarter-hour mark when a clearance on halfway saw Akinyemi escape Ellul and race clear before playing in Bradbury but Mersin came off his line to make an excellent save.
The hosts opened the scoring in the 24th minute, a classy backheel flick from Ben Allen releasing Akinyemi, who lifted the ball over the advancing Mersin for Bradbury to nod in from close range.
Maidstone had been unhappy with a number of decisions from referee Michael Ryan but they appeared to get away with one when Walters tripped Allen in the box.
The visitors levelled in the 56th minute with Ghandour’s second goal in as many games.
Skipper Gavin Hoyte created it with a lovely low cross from the right, following good work by Corne, and Ghandour finished inside the six-yard box.
Powell was denied a penalty soon after and, with the fans behind the goal back in full voice, they began to turn the screw, attacking at will for a spell.
Welling, however, turned the tables and went back in front in the 66th minute, Stevenson taking the ball down in the box and beating Mersin, who couldn’t hide his frustration.
Maidstone introduced Alfie Pavey up top, his first appearance since being recalled from Dover, in search of a leveller.
They pushed, urged on by Hayrettin, but a combination of poor final balls and Welling throwing bodies in the way, meant a second equaliser eluded them.
Welling had a lucky escape when keeper Boyce-Clarke appeared to spill the ball over the line.
And the Wings went straight down the other end and scored an injury-time third when Bradbury found himself in on goal and slotted past Mersin.
Ellul met a corner from Booty to pull a goal back but Welling held on and celebrated safety.
Welling: Boyce-Clarke, Ezennolim, Statham, Shokunbi, Allen (Barnes 78mins), Bradbury, Akinyemi (Matthews 51mins), Sendles-White, Wells, Stevenson (Derry 79mins), Margetson. Subs not used: Pearce, Burnett.
Maidstone: Mersin, Hoyte, Ellul, Fowler, Binnom-Williams, Booty, Powell, Corne, Pattison (Pavey 76mins), Walters (Deacon 69mins), Ghandour. Subs not used: Hadler, Elokobi, Gurung.
Referee: Michael Ryan.
Attendance: 2,015.