Lynn had told his players to be brave in the build-up, and he was courageous with his team selection after moving scrum-half Keira Bevan to 10.
The gamble paid off as the hosts enjoyed a perfect start under Friday night lights and it was fitting that the recently crowned Welsh Rugby Writers’ player of the year Courtney Keight bagged the opening score.
Georgia Evans and Tuipulotu had made the hard yards before the ball was spread wide to Keight on the left wing and she cut inside to go over.
Kelsey Jones’ turnover provided the launchpad for the second, with Evans popping a neat ball back inside for Tuipulotu to charge to the line.
South Africa responded with Felicia Jacobs benefiting from a dominant scrum on Wales’ five-metre line, but that was to be their only score in a one-sided half.
Former Cardiff City footballer Amy Williams came within metres of scoring after winning the footrace to Lisa Neumann’s grubber kick, but Seren Lockwood was first to the breakdown and darted over herself.
It was a double blow for the visitors who had hooker Lindelwa Gwala sent to the sin bin for being offside in the build-up.
Wales took full advantage with Maisie Davies showing her power to score her first international try and secure Wales’ bonus point.
The hosts were in dreamland, but had to revert to their usual half-back pairing when Lockwood failed to return from a head injury assessment, with Bevan going back to scrum-half and Lleucu George slotting in at 10.
The enforced changes did little to halt Wales’ flow with Freya Bell coming agonisingly close from a five-metre driving lineout, but Jones was there to clean up as she crossed over.
South Africa then went down to 13, with lock Danelle Lochner sent to the sin bin for a high tackle on Kate Williams, a card that would later be upgraded to a 20-minute red.
That paved the way for the pick of Wales’ first-half tries. A solid scrum provided the platform for the ball to be worked out wide to Neumann who cruised over from her new full-back position.
It was Wales at their clinical best as they headed down the tunnel 38-5 in front.