45 degree placement in squarish room?

Diagonal placement works quite well in small rooms. Here is a good read on it:

http://www.decware.com/paper14.htm

Also, at the recent Bay area audio show one of the best rooms IMO was DeHavalind, using a diagonal set-up. Roger Sanders uses one too at shows where he exhibits.

They don't need to be equidistant from the shared corner. Using this set-up you can be more flexible in how you place the speakers. Use your ears to judge.

So, maybe the room is 50-60% of the sound after all?

I think it is more than that.