If his old roku is full of channels then he would need to either get a newer Roku or remove a channel to make room for yours. At 70K I think every other channel available is larger than that.
Newer roku's don't have any limitation to the number of channels - they can either use an inserted microSD card for cache channel storage, or they remove and install channels as required on-the-fly based on which channels were used last.
It is more likely that your channel is crashing on his roku because you're using incorrect calls for older devices. (SetPort instead of SetMessagePort) for a screen, or other unsupported features on 3.x firmware.