For a UAS operated recreationally, may altitude exceed 400 AGL? AMA rules state in several places that flight above 400 AGL should be avoided. And close to airports there is a more firmly worded restriction. But away from an airport, and presumably in Class G, what are the altitude restrictions?
This question presumes 14 CFR 101 applies.
Addendum to question: FAA appears to be attempting to impose a 400AGL restriction on 101 operations, without regulation. See the amended AC: https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_91-57A_Ch_1.pdf, stating: Model aircraft operators should follow best practices including limiting operations to 400 feet above ground level (AGL).