Hi Batman!
I am enjoying looking at photos of your layout.
I first built three 6by 8 ft frames, like a bed lattice frame you woud set a box spring set on, then laid in the 2 inch foam, and cut three 4x8 2 inch foam sections into 2 ft by 8 ft sections to make the foam 6 feet wide.
My purpose was if I ever relocated, the layoput being built in 3 sections can easily be taken apart and moved up the basement stairs out the inline door to the garage .The wood legs unboltand come off , making the entire layout easily moveable.
After seing several friends having to cut up and literallydestroying their layouts, I decided what a waste! So I came yup with the bed lattice wood frame and 2 inch foam.
I purchased my foam from a local Menards store and bought more of it whenever they had their 11% off sales.
Even though prices for foam have increased , I got my present stock at much lower prices.
I have about 12 pieces of 4x8 2inch foam on on saw horses in my garage along with about 1and 1 half, and 1 and 1and 1/4 foam 4 by 8 for future use.
I have found it very easy to work with.
I still have a long way to go on my layoutand can easily change things around if I want to.
I may add onto mine later on, but I want to finish up what I have now and not bury mself in another project until I am ready to do so.
Good luck on yours!