GI had inquired about flying subs in the same series (JBL VRX) but was talked out of it saying that the results would be less than desirable.
There are advantages and disadvantages to each approach.
The biggest issue with subs on the floor is simply that some people are close to them and others are far away. The closer seats will be louder-no way around that.
In some cases this is fine (ie concerts-clubs etc), but in a situation like in a church-the goal SHOULD be to get as close to the same sound quality/level etc as possible.
However we have one local large church in which the original install the subs were flown and provided very even coverage.
But they wanted more punch/impact etc from the same number of subs. So we did a test and put them on the floor in the middle. They LOVED it. and they accept the fact that the close seats are VERY bass heavy.
So much so-that in all of their satellite campuses they INSIST that the subs be put on the ground in front of the stage. They say "That sound is part of our DNA".
They are one of those "kick drum worshiping" Churches
It is important that the end user and designer are aware of the pros and cons of flying vs on the ground.
On the ground can provide more punch and impact up close-but provides (in most cases) poor coverage from front to back and side to side.
Flown subs provide much more even coverage front to back and side to side.
Also with flown subs-it is much easier to integrate the subs with the main speakers (assuming the mains are flown) because they are physically together with them.
Sometimes it can be a bit "odd feeling" if the subs are on the ground and the mains flown-as there can be a "disconnect" in the feeling of the sound-even though it may measure just fine. Our ears tell us different.
The lower the mains go in this case-the less "disconnect" there is. If the mains only go down to around 100Hz or higher-then you can have a big "disconnect". At least I do.
I do both in my designs-it depends on what is most important to the customer and I make them aware of the "price" to be paid for a particular layout.