LOL. I had a long post typed out and lost it "doing some research." Long story short, I apologize for the feather ruffling I caused. I spoke to my experience relating to regional mail and did say Hawaii may be different, knowing the spatial relationship between Hawaii and rest of US. I haven't consulted a zone chart in a while and really never paid attention to how Hawaii fit into the zone chart.
In OP's case, USPS regular flat rate is probably the best option and what the post office usually only uses. I know that I see or hear nothing about regional rate mail here. it has saved me a lot of money, but the post office doesn't advertise it anymore.
So, my apologies for ruffling your feathers with my post. I didn't mean to misspeak and did not state for fact about what I said relating to Hawaii. I thought was pretty clear when I said "should" and that anyone wanting to know for sure would research and determine for themselves.
If I knew for certain, I would have said so clearly. Anyway, what is that map thing you referred to?
And yeah, I probably should've looked into it a little more, but I didn't have the luxury of access to my laptop to open 2 or 3 web pages and search zip codes to plug into the zone charts to see how that almost everything was a zone 8.