It seems you have not quite grasped the concept of staging. Buy John Armstrong's 'Track Planning for Realistic Operation. Read it. Redesign the layout. No offense, but as it stands your layout is just a double track loop with some sidings. If 9x8 is the space you have, double track mainline just isn't going to be practical.
I'll clarify.
What's the purpose of the railroad? Because ostensibly you are aiming for more than just running the trains around in a loop. But the point of the railroad is to move goods from one point to the other. It's all in what section of the railroad you wish to model, be it a section of mainline or branch, or a terminus. The railroad exists to move goods from one customer to the other. And since it is wholly impractical to model even alot of the average railroad's customer base, that's where staging comes into play, to act as 'the rest' of the world. And a railroad isn't going to have just a loop of double track main and interchange with another railroad on a spur. That's why I don't think 8x9 is big enough for double track, unless you make the layout a double oval, hide one loop under the benchwork to act as staging, and then simply model a busy stretch on the topside with lots of meeting and passing. Now, Robert Schleicher has drawn a 8x9' double-deck track plan with mainline running as a significant feature, but the benchwoork for it is stupifyingly complicated and costs a fortune in plywood to build, and even then more than half the track is hidden.
Now, I'm not saying that a model railroad has to be 100% prototypical. Heaven knows my plans aren't. But I've built a plan similar in design to what you have here and the scope is not terribly great.