[JamesCH95]

I don't know if you'll like my suggestions... but here goes:

I REALLY don't think you'll want to lag-bolt it down and try to bend things into alignment. I think you will run a significant risk of distorting the tubes that house your gearboxes, and thus screwing them up with misaligned shafts, bearings, and gears.

A few possible paths forward:

Option A
1) Cut the front and rear cross-members in half
2) Use sleeves, blocks, or plates to reconnect the two halves of your chassis
3) Leave enough slop (or better yet, use slots) in whatever connecting part(s) you use to adjust the chassis for flat ground

It will still be fairly strong, but won't conform to variations in playing fields.

Option B
1) Cut the front and rear cross-members in half
2) Connect them together with sliding plates, rod ends, spherical bearings, some combination of these, or something I didn't list that allows relative movement in multiple axes between both halves
3) Mount a flexible 'deck' to the whole structure (1/8in polycarb?) to act as a suspension spring

Perhaps the linkages get complicated and run the risk of binding, but it would somewhat conform to playing field surfaces.

Option C
1) Completely remove the front and rear cross-members
2) Connect the two 'drive pods' with two sheets of a flexible material (again, polycarb comes to mind) on the upper and lower surfaces, acting as springs and allowing the whole chassis to conform to the floor.

My favorite solution of the three, allows a lot of wheel movement (relatively speaking) and could be selectively stiffened to optimize performance. It also provides a lot of surface area for electronics/cRIO, etc.

Best of luck!