Welling recovered from wasting a two-goal lead to earn a crushing win over Forest Green Rovers.
United led when Doug Bergqvist fired home from close range and Loick Pires prodded in a second.
Anthony Barry's 20-yard shot and a Yan Klukowski penalty made it 2-2, but Rovers' Dale Bennett was sent off for felling Lee Clarke and Ross Lafayette scored the resulting spot-kick.
And a drilled Clarke shot and Alex Dyer's strike sealed victory.
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Forest Green manager Dave Hockaday told BBC Gloucestershire:
"It wasn't a bad day at the office. I can't ask any more from my players.
"We've dominated and had loads of chances but their keeper has been outstanding.
"It's the third penalty against us on the trot and I have to question it.
"I don't think it was a penalty and it certainly wasn't a red card. It just killed us."