Ken, I agree with your comment that #6's in the yard take up way too much space. I used #5's. Donald made a great point about the forgiveness in 3 rail operations compared to 2 rail. My track will allow either scale or highrail equipment to operate so tolerances are very tight. The minimum #5 turnouts make the yards accessible to many of the scale wheeled engines. I think the layout looks great as you have it now.
One area I would look at further is the yard to turntable to roundhouse area. All my roundhouse stalls are 23" deep, exterior tracks at the roundhouse vary from 20" to 12". Upscaling by 64/48 gives 30" in O scale, with a shortest of 16". If there were 4 stalls, 2 could be shorter. I can get engines longer than the turntable into the roundhouse because all 3 of the turntable approach tracks line up with a roundhouse stall track allowing engines to be driven directly across it into 3 of the stalls without the need to rotate the turntable.
I have 3 approach tracks to the turntable, two start from a main line, one from a tail track in the freight yard. I find when operating the layout I use the main line approach far more often that the freight yard approach. That might just be my operating style. If I had any great suggestions for how to improve the roundhouse area I would share them but so far I am stumped on how to get more space there.
