[NickE]

Looks good. (Its amazing how much room is left over with all of those Jaguars.)
Where are your relays and pneumatic components going? How is the battery restrained? How thick is the tubing on the frame rails?

The gearboxes look similar to our 2008 gearboxes. Are you using plastic sideplates? Is the rear wheel direct driven?

One thing you might consider to stiffen the chassis is to have the wooden baseplate extend under the siderails (except where the wheels are.)