It was hoped Trent Hemi could repeat his 62-ball innings from overnight, but the other spinner Conor Beleski got him to push forward and spoon up another simple catch after only six deliveries.
The statistics are stark as Wanganui's achilles heel continues to be a lack of a quality spinner for their team, while as batsmen not getting enough time in front of the few who play at club level, with top side Property Brokers United having a patent on all of the decent ones.
In contrast, Sanson was the workhorse for his team with a 20 over spell, bringing fielders in around the bat, while allowing Horowhenua-Kapiti variation as pace men Ramesh Subasinghe and century maker Tharaka Waduge (2-23) bowled with vicious intent from the other end.
And so Wanganui's last man Connor O'Leary walked out to join Nick Harding, who showed incredible restraint to forgo his swashbuckling style, to try and survive at least 13 overs or roughly 45 minutes in the oppressive heat.
Harding, a boundary rope hunter, locked himself down into such a stonewall mindset that he finished with an unthinkable one run from 50 deliveries, while O'Leary (12) took the odd runs to work himself off strike.
For over after over, Sanson, Subasinghe and then Waduge fired it in, with the fielder's appealing for anything that even touched the pads.
The schoolboy O'Leary stayed composed despite a couple of nasty bouncers, and then dug the pace deliveries out of the block hole.
Horowhenua-Kapiti were trying everything, with Harding even stepping back to point out they had brought a second fielder in close without a helmet.
With Sanson bowling, the visitors were still getting through their overs quickly to give themselves more time, and when Harding safely negotiated the spinner's 20th over, the game was reaching its climax at 6.25pm with Waduge lining up O'Leary for what should have been the last time.
His first delivery pitched up straight on the pads, and although O'Leary thought he should have been safe, the umpire agreed with the whooping visitor appeal for LBW.
Horowhenua Kapiti completed an extraordinary comeback for the first outright win despite losing the first innings in many seasons of Furlong Cup.
Disappointed Wanganui captain Rayner had nothing but praise for O'Leary and Harding's gutsy last stand.
"They shouldn't have been in that position, but it was a good effort from them."
The game had come down to sessions and although Wanganui had dominated the first two, Rayner sensed from after lunch on Saturday that the visitors were a different team, easily claiming the next four sessions.
That momentum led them to go wild with the bat on Sunday morning, with Waduge surviving a dropped catch in his teens to go on and make an excellent 117, leading the way as Kinnerley, Ryan Slight and especially Hemi took some serious punishment.
"From that dropped catch this morning early on, it set the tone for the day," said Rayner.
"We just didn't get our length right, a lot of runs square of the wicket. You can't do that on the second day."
Rayner also had to acknowledge the need for a spinner, with the pace bowlers tiring in the heat on a flattening pitch with an older ball.
"That did limit us in what we could do in between the seamers."
Funnily enough, the 1st innings advantage was still enough to keep Wanganui ahead of Horowhenua Kapiti in fourth place on the Furlong Cup points table, with this season having a new bonus points system for reaching milestones with bat and ball.
Taranaki still leads Wanganui's next opponent Hawke's Bay despite losing on first innings to them the previous weekend, while Manawatu remains in third despite a first innings loss to Wairarapa.
Scoreboard
Horowhenua-Kapiti 1st innings
M Good ct G Smith b R Kinnerley 9
T Waduge ct D Rayner b R Kinnerley 17
K Fahey ct M Boswell b R Kinnerley 4
D Sanson b R Kinnerley 14
R Lorimer b R Kinnerley 0
R Taylor ct M Simes b C O'Leary 9
R Subasinghe ct G Smith b C O'Leary 11
R McCone ct D Rayner b C O'Leary 49
K Monk ct N Harding b R Kinnerley 28
D Kennett not out 6
F Bartholemew lbw b R Slight 0
Extras: 28
Total: 175 (54.3 overs).
Bowling: R Kinnerley 18 overs, 7 maidens, 48 runs, 6 wickets; R Slight 11.3-2-29-1; T Hemi 12-3-31-0; C O'Leary 11-0-54-3; N Harding 2-0-6-0.
Wanganui 1st Innings
M Boswell b R McCone 0
DL Rayner ct & b K Fahey 57
G Smith st R Lorimer b C Beleski 39
M Fraser ct D Sanson b R McCone 8
C Stewart ct M Good b F Bartholemew 13
M Simes ct D Kennett b F Bartholemew 3
J McIlraith ct D Kennett b R Subasinghe 32
R Kinnerley ct K Fahey b F Bartholemew 7
N Harding b R Subasinghe 33
T Hemi not out 2
C O'Leary ct R Lorimer b R Subasinghe 4
Extras: 37
Total: 235 (57.2 overs)
Bowling: R McCone 8-0-20-2; F Bartholemew 12-2-54-3; R Subasinghe 18.2-3-66-3; D Kennett 6-1-26-0; C Beleski 9-0-37-1; K Fahey 3-1-14-1; R Taylor 1-0-1-0.
Horowhenua-Kapiti 2nd Innings
M Good b R Slight 28
T Waduge b R Kinnerley 117
K Fahey b C O'Leary 6
D Sanson ct D Rayner b C O'Leary 1
R Lorimer lbw b C O'Leary 0
R Taylor b R Kinnerley 69
R Subasinghe ct D Rayner b T Hemi 46
R McCone not out 44
K Monk not out 13
Extras: 10
Total: 334-7 dec (47 overs).
Bowling: R Kinnerley 9-0-69-2; R Slight 4-0-36-1; C O'Leary 10-1-47-3; T Hemi 10-0-95-1; D Rayner 5-1-20-0; N Harding 7-0-47-0; M Fraser 2-0-16-0.
Wanganui 2nd Innings
D Rayner ct T Waduge b R McCone 0
M Boswell b R McCone 5
G Smith ct R Subasinghe b R McCone 0
M Fraser b D Sanson 37
C Stewart lbw b R McCone 1
M Simes b T Waduge 11
J McIlraith b C Beleski 29
R Kinnerley ct R Taylor b D Sanson 22
N Harding not out 1
T Hemi ct T Waduge b C Beleski 1
C O'Leary lbw b T Waduge 12
Extras: 9
Total: 128 (48.1 overs).
Bowling: R McCone 5-2-6-4; F Bartholemew 3-0-11-0; D Kennett 1-0-2-0; D Sanson 20-6-58-2; T Waduge 5.1-2-23-2; R Subasinghe 8-2-16-0; C Beleski 6-4-6-2.
Result: Horowhenua Kapiti won by 146 runs; Wanganui win first innings points.