I've never had a problem with this. I suspect you are traveling out earlier than absolutely necessary? When I start dropping the traveler (upwind), we're double trapped and trying to keep the boat footing. Even if the traveler moves a little when I sheet in, I'm sheeting in to power up (so it's OK) and it will drop right back to where it was. At the MOST, I drop the traveler 8 inches from center if sailing upwind in really windy conditions. I just haven't ever really noticed it moving when I sheet.

One other thing that comes to mind - the further forward you trapeze will reduce the side force on the traveler as you sheet in. Perhaps you are trapping too far back?