I estimated that you need about 100" for a semi-scale steamer and six car train. You have about 150" of straight to work with in the O42 loop. The Ross Reg 11° are 14.65" long or 29.3" total.
Placing the switches in the O42 loop just past or at the curve will give you the maximum straight to work with.
The 11° can handle a good speed for crossing over.
here's 12- GG 10"