So you might have heard it through the grapevine that your mix session should not peak anywhere above -6 dBFS before the final mastering stage.
Obviously if you decide to follow that principle then your kick should peak at -6 dBFS whilst your bass peaks from -10 dBFS up to -6 dBFS. It’s just an artistic guideline but not a science – (…deep sigh…).
Generally speaking there shouldn’t be issues for your bass peaking at -6 dBFS especially if we are talking about things like 808 kick drums or if you are mixing for bass heavy genres like reggae, drum & bass and so forth.
But as for other styles of music to have your kick at -6 dBFS and your bass at that same -6 dBFS level is definitely asking for trouble.
Instead if a mastering engineer is given a such a track were the kick is at -6 dBFS and the sub bass at -6 dBFS, and that doesn’t fit the context of the genre in question, rest assured the subs down will be attenuated appropriately.
Remember in an ongoing era of loudness wars too much bass means you can’t beat the competition!