Legal regulations for eBikes

Hey everyone!

Been thinking a lot lately about the legal side of our eBike passion, especially for those of us who love to tinker. I've got a custom-built fat tire eMTB, and while it's a blast on the trails, I sometimes wonder about the line between a legal Class 1/2/3 and something that might get me into trouble, especially with the mods we all love to do. What are your experiences or insights on how DIY modifications (like upgrading motors or batteries) affect the legal classification and regulations in your area? Is it a "don't ask, don't tell" situation, or are there clear guidelines?