Becky, if you aren't already doing it, you can probably eliminate most of that wobbly factor by being sure each star is flat and square before you ever join them. I always do this with starch as I finish each block.

Thanks Teri! I tend to think about BIG quilts!

You can also use Margo's technique on the ironing board with a ruler & pins that you can press to line things up correctly. Follow Margo's directions and press. This should help.

Whether or not you have already attached the star border to the center, you may be able to flatten it some by blocking it. Mist the entire quilt (or the just the borders if they aren't attached yet) with either plain water, or a combination of water and liquid starch, and let it air dry flat. That should take up some of the wobbly parts. I lay mine out on the floor and gently press the fullness with my fingers to make it as flat as possible. Don't move it until it's completely dry. Then press (up and down with no side to side movement of the iron) with a hot dry iron. Let us know if it works for you! Be sure that when you add the next borders that you take your measurements from the center of the quilt, not the outside edges, which would just compound the issue! Then ease in any fullness that the blocking didn't take care of. Let your feed dogs help ease in the fullness by stitching with the stretched fabrics on the bottom.

Also, for future reference, starching your fabrics before you ever cut out your patches will help minimize stretching the bias seams. Although these tutes are for last year's BOM, I show how I starch my fabrics on my Webshots tutorial. Here are a couple of links:

http://good-times.webshots.com/photo/2233147680102889971HfruOw

http://good-times.webshots.com/album/569871038PKjhFR

my star border is a bit wobbly. Do you think that when I quilt it, it will flatten out OK? basically, the outer triangles are stretched out. apparently, I didn't handle them as carefully as I should have.
thanks - becky