Sounds like flight training to me. The 50 mile exemption should work for a while. I don't think the 90 day exemption applies because an ELT was never installed. Eventually you'll have to spring for a 406 ELT. Last time I looked, ACK Technologies was still the cheapest at $600 from Spruce. Many people would regard a 406 personal locator beacon as safe, but it's not a legal replacement for an ELT.