From an earlier Post.....
Going to share a problem with you that I ran into on my first attempt of attaching squares on my other BOM quilt. One of my squares that I quilted the top squared pulled in some because I forgot lengthen my machine stitch for quilting instead I had been doing PP and I was using smaller stitching. So I figured if I went a head an squared up the block to match the other blocks at 12.5 I would be ok. Now I had about a 1/4 of an inch batting showing all the way around a few places a tad bit more in some. " So Im thinking to myself that the sashing will cover up my goof. Well for the most part it did. However there was still some batting that showed through I ended up pulling out my stitches (frogging) and had to rework my square. So I would recommend before you even start attaching your units if you have any batting showing you trim all of your squares down so they are the same size and there is no batting showing and don't forget to sew less than a 1/4" around the edges to help secure your quilted stitches. Just a thought and experience I wanted to share.
In retrospect I chose to trim down the other blocks of my BOM because trimming an extra 1/4" round all of the blocks did not take away from the pattern of the blocks. I didnt remake the block because If I had with it being my BOM I felt I was losing some nostalgia of doing one block a month with my friends on the QB . In other circumstances though I think it would be a better choice to remake the block instead of trimming down all the other blocks.