How joule creep would affect my airsoft gun?

Hey! I have a Cyma CM.045A, and I was wondering if I can use it on airsoft fields in my country. Most fields are restricted to 1.5J, and my replica had a paper in the box, which says it was tested at the store at around 392-398 FPS with .20g BBs, which means ~1.46J. I would like to know if my Joules would get higher with .28g BBs, and if it was still allowed to use, but I don’t have a chrono to test it. Thanks!