It would seem that a full voice can be achieved by: 1. reducing the tension on the soft upper pallet, which gives the vocal tract a slightly longer tract, as the soft upper pallet can then be more concave upwards. This gives bassy sounds a longer path. 2. Then, send (push) the sound more to the sinus mask to increase higher frequency resonance as well. Curious as to whether this idea is correct. Love to hear your thoughts!
This is not to say that it’s easy to detense and push at the same time, while there’s still vocal tract tension. Vocalposture’s view is that eventually, detensing will make the full sound the natural, innate sound.