Fred and Mike,
Use shims of 0.10" white styrene on the outside rail. I have done this a lot in N scale. Any thicker and you get that flop over Mike is talking about. And start the "super-elevation" about 4" into the curve, let the track "float", don't nail or glue this area down, from there back to the straight part and fill this air space in with ballast. The shims are cut from 1/8" wide strip styrene about 2" long and placed under the outside rail only and glued to the cork roadbed.
I tried to put the shims under the cork once, and as you can imagine, this did not work well since only one half was tilted and it left a dip in the center at the joint of the two halves of cork. The shims work better with the stiffness of the flex track.
Now if you really want to get rediculous, you could start with just the cork glued down and then, using a plane, shave the tilt into the cork itself.....but then you would have a dip where the curve met the straight. Or you could plane some balsa or basswood sheets cut to the proper width of the cork roadbed and also to the right curvature with easement incorporated, and then you would have a super-elevated base on which to lay your cork and track.
Nah! Stick to the styrene shims.
B-)