If you're using subs, you can put the main four π speakers up a little higher. You'll still want to make sure the floor bounce notch is within the subwoofer's bandwidth, so it will sum with the mains and smooth out the notch.

To make best use of subs, you should carefully consider placement of the mains and the subs so the summing of each together forms the smoothest overall response. Also relevant is the bandwidth of the subs, because the can smooth the floor bounce notch from elevated mains only if the frequency of the notch is within the passband of the subs.

In general, the closer the subs are to the mains, the higher in frequency they can be run. There are competing proiorities though, because best room mode averaging is provided by distributed subwoofers. You want to position the subs where they smooth room modes best, i.e. constructive nodes from one bass sound source should lie where destructive nodes from another bass sound source falls. So as you can see, there are a few variables to juggle when deciding the best positions and subwoofer bandwidth.