I drafted a pattern for Lina by getting online pictures of pants patterns. I did one with no side seam with the legs as single pieces. The key to the crotch curve is that the straight parts of the curve should be on the grain.
http://www.make-baby-stuff.com/baby-...y-pattern.html was my starting point.
The waist I did as 1/2 her widest point + an inch.
I did use her stretch pants to help mark out the crotch curves for the first try. I started by marking things directly onto cheap fabric. Took a couple tries to get it right and once it was right I traced the working version onto cardboard.
I posted pictures of the pants in the show off the clothes thread.
http://www.flickr.com/photos/sapphire_chan/3483581700/ is the first pair that worked, you can see that they managed to fit fairly well even with her diaper needing to be adjusted.