The pair had a net round of 61, 10 under par, and won by a single shot from Ratho Park's Andrew Erskine and Bob Wills. Rennie won a cheque for 500 and Erskine received the 350 runners-up cash prize. Rennie and Anderson will go forward to the Grand Final at Sandals Resort in the Bahamas from 23 November.
Elsewhere, Northern Counties team player Anne Ryan (Tain) leads the field by one stroke in the Scottish senior women's (closed) amateur stroke-play championship at Fortrose and Rosemarkie Golf Club.
Ryan shot a three-over-par 74, including birdies at the sixth, seventh and 15th. The CSS was 73. Her closest challengers at the start of the second round - at the end of which the leading 16 go forward to the match-play championship - are Fiona De Vries (St Rule), a shot behind on 75, and joint third-placed Lynne Terry (Cruden Bay) and May Hughes (Lanark) on 76.