That's interesting, although I was considering the effect of 2 different kinds of subs.
I read something of recently on 'hometheaterforum.com' that advises against that. And also that 2 of the same subs work best in the same location.
In other words, if you find the best location for one sub, use the same location for 2.
I orignially thought having 2 in 2 different locations might actually compensate for any deficiences in response due to the room itself.
Maybe that's not really a significant if one sub is properly 'located'.
Obviously, 2 in the same location will give more output.