Can I have back to back O96 curves on my layout?

At that wide of a curve, I don't know of any equipment that would have issue. Minimum is often O-72 so even an S curve as you may be implying at 96 is very gradual.

Assuming you mean creating an "S" turn with your 096 curves, one left followed by one right, that should work.   I believe John Armstrong covered S turns with 2 recommendations,  the preferred configuration is to have a straight section between the reversing curves of at least the length of your longest piece of rolling stock, ie. 21 inch passenger car.    However, I am 99% sure I remember him also stating that if you don't have room for the straight, then the 2nd best option is to go directly from the left hand curve to the right hand curve with NO straight section at all.   

096 is the minimum curvature on my layout,  I have one spot where I have an S with no straight track between them and it runs fine even with long passenger trains (21 inch cars).   

If you have some longer modern freight, or passenger cars, I'd recommend you just set up a test section and push pull some long cars through, paying attention to how the couplers react.   Typically the longer the car, the longer the overhang from wheel truck center to the end of the car frame and coupler knuckle  so they tend to swing in opposite directions going through the "S". 

Hope that helps

Thanls for your replies.  Actually, I was just asking about two large loops, one inside the other, that will have some straight track between the curves.  I do run a lot of large coaches, including some heavy K line coaches so I have been trying to avoid the S curves. 

Here are some solutions...

This is the concentric, commonly-used 84 track nested in the 96, with approximate 6" track spacing, taking up roughly 108" of layout width:

Here is one-of-many solutions for nesting two 96 curves (back to back) using four (4) 5" straight track sections for the outer curve:

Admittedly, it is not optimal in keeping a consistent spacing between the tracks but it will give you an idea of the strategy to use two 96 Fastracks in concentric curves. Many other solutions are possible.

Thank you.  Yes, I am bothered by the lack of consistent spacing between the curves and hoping for a better solution.  Could I add some small straight pieces in between the O96 curved pieces to create a larger curve or will that cause other problems?

No problem adding and using smaller straight sections to create the smoother curve. Add as many straight sections as you like. 

Awesome.  Thanks for your input.  I will give that a shot.