Playing stride left hand without looking is a great way to firm up your sense of where things are (I hope Ted will be pleased with me). That's how I got comfortable with this. Another thing I did at the time was to play everything without looking, not just my target piece. This can give a big boost to sightreading, because looking up and down a lot is an obstacle to reading. If the eyes are free to keep looking ahead, there's more time to take in information. Now I look or don't, as I wish, because that short time of concentrated effort really worked for me. Anyway, good luck.