i have faith that my sub will project given the particular frequency content that's already associated with the sub bass.
my biggest concern is accurately representing the sub bass frequency in relation to the audible content that is provided by the bass.
That being said, you can relatively have a sub bass at most keys, due to the fact that you're covering your overlap in the audible realm.
in order to get a more audible sub bass, it requires layers of distortion and or (one to a few) layers of audio that varies in waveform.
of course you should process the layers accordingly so that they fit as one cohesive element.
I also don't stray far from the F, G, C keys when writing music.