If you've used a size 5 in Judo Gis, an A3 is usually the Brazilian sizing equivalent. But if you're saying that even your old size 5 Judo Gi was a bit too big then maybe you might want to try a size A2 then shrink to fit as necessary. Also, most BJJ Gis are cut to be slimmer or less baggy at least when compared to Judo Gis. Its just a part of the unique style of Gi for BJJ. Hope this helps.
thank you.........