Just thinking here.... but are you going to secure the tuning plates somehow, or just let them slide? If you find a trailer (and maybe a forklift) that you want to mount it to or carry it on, it might help to prevent the plates from moving after you have figured out the tuning.
I am sure you have it worked out though, it is really coming along.
UDS, 30 Year Old Kettle, I need to build something bigger. KCBS CBJ