Virtually all Left Handed Hitters experience this. Adam Dunn's Flyballs from left to right (career) 69.7%/53.5%/31.5%, Russell Branyan 75.9%/60.4%/28.9%, Raul Ibanez 57.3%/39.6%/22.5%. The same effect happens to right handed batters too, when they pull the ball, hitters are simply more likely to hit it on a lower plane, the effect isn't unique to Kotchman. Yes, he may lose a hanging double or two down the left field line to the wind, but he's also likely to see a handful of his flyballs to right turn into homeruns and overcome that loss. Really, he stands to benefit more from Safeco than Russell Branyan did, because Russell Branyan is likely the same or better at parks that are more evenly distributed (this isn't to say that Kotchman will perform better than Branyan did) as he won't lose as many homers to left and probably wouldn't lose any to right.