RE: No "Hi/Lo" with <span class=
To my knowledge, Futaba is the only manufacturer that recommends you keep your crystal changes within a certain band. FMA, Hitec, Airtronics and JR make no such demands. However, as an electrical engineer, I can almost guarantee that any one of these units would benefit slightly by being tuned for their specific crystal being used at the time. It just happens that they usually fall into a safe operating area and are close enough to get by and meet stated specifications.