I've done FMQ on just three lap quilts and on the second one discovered after I was done that I'd left the feed dogs up the entire time. I didn't notice a difference at all, so that's one of the things I'm not going to worry about. Also I figure that variation in stitch length is not such a big deal unless I've got a stitch that's reeeeeely long in which case I'll just go back over it. Thanks for posting the photo of your practice square - I think you're doing just fine!