The %ActiveTemplateInstance parameter was your problem, since it uses the number for your template there, not the number for the resizer template. Since there can only be one resizer template anyway, you can simply omit it.
Thanks for the suggestion, but I had tried that when I posted, but forgot to mention it, and it didn’t work, but maybe I didn’t do it right… I just tested it and it DOES work.
I found code in an old template of mine that worked:
Yep. I’m pretty sure this code originated back in C6, maybe it wouldn’t accept an omitted parameter? Probably 20+ years old, so I have no idea any more