Pinewood Derby Track

Rough model of a pinewood derby track I plan to build from 1/4" MDF.
Loosely following this guide:
http://www.waynesthisandthat.com/pinewoodderbytrack

Track should be easily disassemble-able into approx. 4-ft long sections, to allow for portability.

Finding 4ft x 8ft, 1/4" MDF and/or Hardboard is near impossible. I bought 1/4" MDF for the lanes, and for the track surface as a whole I just used whatever approx. 1/4", 4ft x 8ft sheet material I could find, that would comfortably make the 26-degree transition from downhill-to-horizontal within a single 4-foot length.

This is the MDF I'm using:
https://www.homedepot.com/p/1-4-in-x-2-ft-x-4-ft-Medium-Density-Fiberboard-1508104/202089069
https://www.homedepot.com/p/Handprint-1-4-in-x-2-ft-x-4-ft-Medium-Density-Fiberboard-354221/202093850
* I think those are the same item. Not sure why it's listed as two separate items on HD's site.
Frustratingly, they don't appear to exist in 4ft x 8ft sections. With a narrow sawblade and a steady hand, you should be able to cut all the lane pieces from 3 of those. That's 8 track sections (the ninth is a brake section), with 4 lanes each - 32 lane sections total.

Whatever track-surface material you end up with, you should be okay with 2x of the 4ft x 8ft sheets.
I ended up using 5mm underlayment for the track surface, on which I attached the MDF lanes. The underlayment is lighter, thicker, less floppy, and more dimensionally-stable-under-sunlight than hardboard. This is the underlayment I used:
https://www.homedepot.com/p/1-5-in-x-4-ft-x-8-ft-Hardwood-Plywood-Underlayment-Specialty-Panel-431178/203183010
Two of those 4ft x 8ft sheets should be enough.

For the ramp framing - just use whatever's cheap.

For the springs on the start gate, I used these:
https://www.homedepot.com/p/Everbilt-1-4-in-x-1-1-2-in-and-11-32-in-x-1-7-8-in-Zinc-Plated-Extension-Spring-4-pack-16086/202045462
For the screen-door handle/latch on the start gate, I used this:
https://www.homedepot.com/p/IDEAL-Security-White-Painted-Storm-and-Screen-Door-Pull-Handle-Set-with-Back-Plate-SKDXW/203553462

Lane spacing is specifically chosen so that it's possible to glue 3 standard pinewood blocks together side-by-side, to create a 1.25"-tall, 7"-long, 5.25"-wide block, which will perfectly straddle two adjacent lanes, with the same clearance a 1.75"-wide standard block will straddle the single lanes.