I use the zig zag foot that came with my PC420 and just move my needle till it I get a 1/4" seam when aligning the fabric with the right side of the foot. Both the 1/4" feet that Brother says are compatible with my machine cause the same problems Geri B noted for her BL (Baby Lock?). I find that I get a very accurate 1/4" seam on the PC420 just by using an index card to determine where to position my needle in relation to the rt. edge of the zig zag foot. I also try to use 50 wt. thread and a 75/11 needle which helps reduce bulk in the seams when they're pressed to the side. I have found that sometimes for blocks (like star blocks) where you have to be super-accurate with your piecing to get nice points I have to do some fine-tuning with either fabric positioning or needle placement, but for most piecing my zig zag foot works fine.