After a little bit of head-scratching, I decided on how to transfer the Elizabeth Valley Railroad trackplan to the layout panel. That's the end result in the opening photo with some buildings placed for scale.
That's the 2' x 3' trackplan before getting started on the transfer.
I started by drawing a 6" x 6" grid on the panel with a Sharpie pen to match the grid on the plan.
I then taped the plan to the panel and used a circle punch to cut holes at various places. I just carefully pushed the punch into the paper until a hole was cut. Each hole was then marked on the panel with a Sharpie pen. At first I thought I could transfer the plan to the panel by sandwiching a graphite sheet between plan and panel, and then trace over the plan with a pen. I tried it, but the plan didn't transfer. The cork had too much give, and no marks could be left by the graphite paper.
If you look closely you'll see all the dots on the panel - but you have to look close :-)
That's a close-up. A dot cloud in this view.
At this stage I connected the dots with help of the plan, a ruler, spline, and the good, old Sharpie pen. The grid makes it a little easier to figure out how to connect the dots when you're comparing them to the plan.
And that's what it looks like with all the dots joined. I'm expecting that once I start laying down the track, I'll have to make some adjustments so that things roll smoothly, so the plan is just a starting point to get the general positioning right.