What size did you
have installed before? If it was a 135 then there should be no problem. The "test" is put the car in the middle of the track and unfurl the jib. The jib sheet running from the track car to the clew, should bisect the angle between the foot and the leach. You want to be able to move the car forward to "pull down on the leach" more or move the car aft to "pull back on the foot" more. The "car aft" position is for higher wind speeds, the "car forward" is for lower wind speeds. My guess is you are trying to "go faster in light winds by using a bigger sail". So the clew moves aft and the jib sheet lead looses its ability to "pull aft on the foot" and increses its ability to "pull down on the leach, all relative to a smaller sail. So you are losing the ability to flatten the sail in higher winds. Prepair to heel.You can always augment the jib sheet lead with a barber-hauler. Not a great answer but more options is usually better than fewer ones.