AMA allows flight outside of designated airfields and over 400' if outside 3 mi. radius of an airport. And if you use AMA, not all of it applies anyway since it is written for different types of craft primarily.You cannot, because the part that keeps intentionally getting left out is the "following community guidelines" stipulation of Section 336. That means you can either follow the FAA guidelines (which includes the 400ft rule) or you can follow some other group's guidelines (like the AMA's, which only allow flight at AMA airfields). What set of community guidelines are you following that allow flight above 400ft?
And, again, Part 107 does not apply, as the FAA categorizes a hobby flier by Webster's Dictionary only. The FAA defines you by WHY you fly, NOT HOW you fly.