J.,
I like what you did with the Gold line entrance and exit. The previous location of one pair caused a lot of fitment problems. This get the job done!
if you want to build the back Lavender loop on the hill, 15 1/2" would act as a placeholder for the O72 switch. One combo is a 10" + 4- 1 3/8".
I agree with Jan, try to smooth out the spurs whenever you can. You need to put some uncoupler tracks on your shopping list.