Wow, these are very helpful responses. As you can tell, I've never made a wall hanging.
I had the idea the batt had to be poly because it would be light in weight. I usually use Quilter's Dream, but it seems too soft for this. WN seems stiffer, so that would likely help.
I always prewash fabric. I guess I lost sight of the idea of the shrinkage being the batting. I could prewash it for sure. I know I've read ideas about doing it here on the board (at least, some ways Not to do it!)
I wish there were a way to post pictures here that wouldn't end up outside the board. This will be sort of an "awwww" design (no matter how it turns out, technically!) and it would be disconcerting to bump into it online. I would love to share it with the board, once it's done, were there a way to leave it here.
Thanks for reaching out to help, and I'll be eagerly watching to see if others have ideas to share.
Hugs,
Charlotte