I've been making these and they are selling like "hot potatoes" if you'll excuse the pun. But, I do include a disclaimer about scorching, etc. indicating that microwaving over 7 minutes can cause this problem.
I like the idea of cooking for 4 or so minutes, let it rest, then finish cooking. I'll change the verbage on my instruction sheet.
I love my bag. The potatoes turn out perfect -- fluffy and soft. Sweet potatoes are awesome made this way. I only use 100% cotton materials - fabric, muslin lining, thread. This reduces any potential fire hazard. I do have the applique design if anyone is interested.