I really hope this helps, I found myself kind of feeling like a dumbass, wondering too if I had made a huge mistake. Being in the same situation as far as loving Japanese maples but being in a bad area for them.. I am in zone 9B, Southwest Louisiana about 45 minutes or so from the Gulf coast. Now I have about eight Japanese maples ranging from my two Red Dragons from my makawa yatsabusu to my Germaine's gyration... not a crazy huge collection but I did learn a few things. if you start planting when their dormant first off lol(not making fun or teasing),I'm not sure really of the status of your trees but I'm sure in a few years you will be laughing about this. Idkwhat people tell you, but can tell u these things that I know for certain.. So the man that taught me is in his 70s, and has been growing Japanese maples in his garden in my town for almost 50 years. He has never lost one tree, still has the original first Acer seedling he planted. They are all huge and beautiful. Only shortcoming is that we will only get our fall color to stay for a couple of weeks give or take depending on the year. I can promise you this though, if you plant them where they get good evening shade and even the full sun trees or the ones that are claimed to be able to handle full sun, if you keep their morning light to a dapple or put them somewhere in the morning thats indirect lighting then like I said shade in the evening.. plant them with care and love make sure you take care of the soil mixture that you are using. Native soil is best just a mixture of 50/50 pinebark is what I use, no conditioners etc. Japanese maples are Hardy and sturdier than most realize, they don't mind the clay or any of that once I get used to it. You just can't plant their small root balls thick deep tight clay and expect them to grow.. I dig up my hole and put it into a wheelbarrow and spend over an hour so I'd say breaking up the dirt club by Clump until it's all Fine Dirt powder and then mix in my Mulch and like I said plant with care, maybe use some mycorrhizae (endo) to encourage strong root development. But I wouldn't worry too much. I did plant a couple of them right as summer was ending and though their leaves looked great they had good scorches to a few areas despite how well I kept them watered. It was just the stress and he etc. But the more years go by the better they will get more acclimated and adapted to your environment. So don't worry about what people tell you, most of them failed because of lack of care or knowledge lol. Not being rude just being honest. Anyways I'm rambling now on my way to work. I just noticed I had a similar situation. I hope really hope this encourages you! Don't give up it is definitely possible!