[AdamHeard]

I would reccomend attaching the two parallel rails on each side directly to each other. If you attach them in two places, between the center wheel and each outer wheel, it won't interfere with your plan for ramp climbing.

Also, if you plan on using this frame next year, and the game is rampless, I would connect the two rails in the front and back as well.

Looks like a good start though.