The winger's double-intervention in the second stanza gave the home side a slightly flattering scoreline after the visitors, who missed two conversions and were right in the mix heading into the final quarter of the game.
The home side raced into an early 21-point lead, but the Leopards came back strongly in the second half. At 26-20, with 20 minutes to go, it was anyone's game, but Lewis scored twice to confirm victory.
The Lowvelders had opened the scoring as early as the fifth minute when lock Stefan Willemse barged over for the opening try, which was converted by flyhalf Chris Smith. Moments later the iSG Pumas were at it again, this time with fullback Devon Williams rounding off an excellent move for the second try which Smith converted to give the hosts a 14-point lead after just 10 minutes.
The iSG Pumas, who were in imperious form, needed just another three minutes to extend their lead to 21 points as flank Francois Kleinhans forced his way over for his side's third try of the night, which Smith converted. The Leopards finally found some solace on the scoreboard when flyhalf Schalk Hugo landed a drop-goal midway through the first stanza.
The Leopards kept things tight and their persistence was rewarded when left wing Jimmy Mpailane dance his way through for his side's first try of the evening, which Hugo converted but the home side doused the visitors flame on the stroke of halftime when hooker HP van Schoor rumbled over in the corner as the sides went into the break with the hosts leading 26-10.
The Leopards fought their way back into the match with a try from No 8 Edmund Rheeder, which Hugo converted and then added a further penalty to reduce the gap to just six points. The home side then found some gas and Lewis danced his way through for the first of his tries, giving the home side their bonus-point before rounding off his second score of the night to practically put the result beyond doubt.
After Smith had converted both tries, the home side had their noses in front with a margin of 20 points and just nine minutes left on the clock. But the Leopards never gave up the fight and some apathy from the home team allowed the Leopards to score twice through replacement wing Keagan Tait and fullback Shane van Rooyen but with Hugo missing both conversions, the Leopards had to be content with just a single point after failing to secure a losing bonus-point.
iSG Pumas - Tries: JP Lewis (2), Stefan Willemse, Devon Williams, Francois Kleinhans, HP van Schoor. Conversions: Chris Smith (5).
Leopards - Tries: Jimmy Mpailane, Edmund Rheeder, Keagan Tait, Shane van Rooyen. Conversions: Schalk Hugo (2). Penalty: Hugo. Drop Goal: Hugo.