I do like Ckcrowl and find that if I sew fairly slow, they work just fine--I'd add two things--with a DP or other curved block that isn't paper pieced, I plan on doing some trimming of the block usually, and secondly, be sure that you are cutting the straight sides of the DP block on the straight of grain so that the curves (both convex and concave) are actually on the bias, allowing for the stretching needed to get the matched edges.