On the Cathedral window are you stitching by machine or by hand....if by hand I just turn back as I stitch you get a feel for the 1/4 in i do not press first. If by Machine I think a similar method would also work, using a spot on your foot as your guide. Hope this is useful information
On the placemats with a bias edge spray starch would be your friend to keep a straight edge.
Judy in Phx, AZ