Dear Rosewind,
That is fine.
However, I can definitely tell when my ESL is in a good place also, but in my own [very humbly said] experience it is the case that the further from a solid wall behind the better. Peter Walker was also firm in his assertion that the speaker should should never face at 90 degree from the wall behind. There is an exception and that is when the speaker is in a doorway to another room, and then you get fine results in two rooms!
Of course the distance from the wall behind has practical limitations for most of us, and I find it much easier to find a good place for one ESL than two, but then I actually dislike stereo.
Stereo in my view should be so subtle that one does not notice it, just as one should not be aware of a sub speaker augmenting a speaker that could well play without.
To the OP, I would say [ever so humbly] that in all probability the best speaker for either a Q II or a 303 is likely as not the original ESL ...
Not everyone would agree, and even then not everyone can place an ESL or two ideally in their domestic setting.
Best wishes from George