A duckunder is ok as long as you're able to duck under it. Had one on a previous layout and it posed no problem. However, in those days I was quite a bit more flexible than I am now. If you're reasonably young, you won't really appreciate this 'til later. On my current layout, I have a lift-out/duck-under at the door: on a good day, it's a duck-under; most of the time its a lift-out. It's just a single track, curved, with no scenery. It provides access to a staging track and also allows run through operations when I just want to run trains for casual visitors. I used flex track on 3/4" plywood and provided very positive and rigid alignment for the ends of the plywood. Lay the track continuously from the layout on one side, across the plywood, and onto the other side. Spike the track down securely and then, using the small spikes that are used for hand-laying track, spike both sides of each rail, on both ends of the removeable section and likewise on each end of the fixed section for at least three ties (pre-drill the ties first), taking care to not push anything out of alignment. Cut the rails with a cut-off disc in a Dremel tool, staggering the cuts if the track is on a curve and making sure that the fixed (layout) portion is back from the edge. The ends of the rails on the lift-out should project beyond the end of the plywood. After the rails have been cut, you may have to reposition the small spikes that hold the rails in line - you don't want the projecting end of the rails on the lift-out to be spiked to the layout. When everything is satisfactory, use a sharp knife to cut the ties at a point directly above the joints between the layout and the lift-out. On a curve,this may put part of a tie on the lift-out and part on the layout. Spike any such ties near the cut ends using the small spikes. Now you should be able to carefully lift out (straight up) the removeable section. The recessed ends of the track on the layout will protect them but the track ends on the lift-out are vulnerable and this section should be stored accordingly when not in use. I used a small plug from Radio Shack to provide power to the lift-out, female part on the layout edge, male part on a wire from under the lift-out. This contraption has been in use with very little attention for over ten years. Hope this is of some assistance.