Kris, Hibiscus rosa-sinensis is a Tropical Hibiscus and no amount of protection could save it in zone 6a during winter months. Temps are just too darned cold for it to survive. I tried it here in z7 one year in a very protected, southern exposure bed and it croaked.

I have had success pruning them back in the fall and placing in a south-facing bedroom to overwinter. They look pretty ratty for the most part but if kept watered, they bounced back in the spring when taken back outdoors to a sunny exposure.

Here is a link that might be useful: Hibiscus rosa-sinensis