Hi,
I just went and looked at your shop and Wow! Your work is great.
So sorry to hear that your having shipping issues.
I have a method that I've used with great success, no damage claims with over 400 pieces shipped, half of them large panels, a dozen or so of those shipped internationally~~~~ its kind of tricky and time consuming but its worked for me.
After wrapping the panel/suncatcher with paper than layering with bubble wrap a couple of times, I'll measure and cut sheets of cardboard just a little bit bigger than the bubble wrapped item and layer the piece within it like a sandwich--the cardboard/panel/cardboard sandwich then gets taped together. For the bigger panels I'll use two sheets below and two on top for added strength.
I'll find a box that's at least 2-3 inches bigger then the sandwich all the way around and deep enough to allow at least 3 inches of dunnage beneath the piece and at least 2 above it. A lot of times I'll have to make my own box, cutting down tall ones to my needs.
For the box itself I'll cut another sheet of cardboard to give it a second bottom, cut either cardboard corner reinforsements to add pieces of cardboard to the inner walls of the box. Newspaper is what I've always used as dunnage for large panels. I'll crumble a bunch of it into balls and create a 'bed' of it in the bottom of the box. Next, the sandwiched panel goes in and newspaper gets stuffed all around it until it can't move. Followed by another layer of crumbled newspaper and a sheet of cardboard on top of that before sealing the box down.
I've always thought to photograph the process and blog it, just haven't gotten to it.