You are not the first one to have trouble with ES in zones colder than 6. While advertised to do well in such climates, they suggest winter protection. To provide color, there are two Annabelle clones that could research, Invincibelle Spirit (the one you are talking about) and Bella Anna. They are too new to recommend or comment since few people have had them for long. Some have not been impressed by the I/S flopiness; others did not like the pink shade of color so check them out first. Some liked the color on Bella Anna; no info on stem floppiness yet.

Here is a link that might be useful: Invincibelle Spirit Comments

Thanks for the heads up on the Invincibelle Spirit. I read the posts, and it sounds like a disappointment, overall. Hmmm . . . Maybe the Bella Anna or Vanilla Strawberry. I'm just wondering when the label says "full sun to part shade", if an area that is shaded until about 1:00 p.m. would be conducive. What do you think?

Afternoon shade is a requirement on the southern half of the country. The leaves suffer from sunscorch if I do not give them shade. In the northern half, you can grow them in more sun. In the NE which I visit often, I see mopheads getting quite a bit of afternoon sun. I also see other varieties (paniculatas) growing in full sun in tree form.

When you are not sure, the best thing to do is drive around and try to locate other arborescens like I/S & Bella Anna & Annabelle or other paniculatas like Vanilla Strawberry. Observe how much sun they get this time of the year. You can also go to city/state botanical gardens, arboretums, etc and see how they plant them. And of course, there is the local option.... stop by local nurseries that have a good choice of hydrangeas for sale in May.