here was a very interesting hand, i shared it in my skype group and still cannot determine a definitive line/answer.

villain playing 19/15/ 7.9% 3bet and 12 AF over 308 hands.

raised flop 1/6 times (small sample)

plan was to call down, but river sizing made me change my mind. what to do what to do........
Poker Stars, $0.10/$0.25 No Limit Hold'em Cash, 6 Players
Poker Tools Powered By Holdem Manager - The Ultimate Poker Software Suite.

BTN: $15.30 (61.2 bb)
SB: $25.35 (101.4 bb)
BB: $25.75 (103 bb)
Hero (UTG): $47.55 (190.2 bb)
MP: $27.88 (111.5 bb)
CO: $39.44 (157.8 bb)

Preflop: Hero is UTG with K K
Hero raises to $0.75, MP folds, CO calls $0.75, 3 folds

Flop: ($1.85) 2 7 Q (2 players)
Hero bets $1.25, CO raises to $3, Hero calls $1.75

Turn: ($7.85) J (2 players)
Hero checks, CO bets $4, Hero calls $4

River: ($15.85) 9 (2 players)
Hero checks, CO bets $12.25, Hero folds

Results:
$15.85 pot ($0.71 rake)
Final Board: 2 7 Q J 9
Hero mucked K K and lost (-$7.75 net)
CO mucked and won $15.14 ($7.39 net)