No one replied!? I would say it sounds good. We have a koi pond and I would love to be able to put our RES in it but it gets very hot...last summer the water temp approached 90 degrees for several days. Make sure the water temp stays in the correct range. You may want to look into a filter set-up, too, even at that "small" size.
Also-watch out for exposed liner hazards...RES may try to eat loose edges, that sort of thing. And you may want to get some fish. I am not an expert on what kind to get but there are some (plecos??-cannot remember the name) that are LIGHTNING fast and can outswim the turt, which gives the turt exercise and stimulation. And just know turts are very destructive with plants. Whatever you put in or near WILL be munched so make sure it is not poisonous or something you really care about. My RES loves a water hyacinth treat every so often.
That's all I can think of right now...sleepy. Good luck! Wish I could do the same with our girl....